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LIBRARY 
UNIVERSITY OF ILLINOIS 
URBANA 


FieLp Museum or Natura History. 
PUBLICATION I71I. 


GEOLOGICAL SERIES. Vo. IV, No. 3. 


NEW TRILOBITES FROM THE 
MAQUOKETA BEDS OF 
FAYETTE COUNTY, IOWA 


By 


ARTHUR WaRE SLOcoM, 
Assistant Curator, Section of Invertebrate Paleontology. 


OLIVER CUMMINGS FARRINGTON, 
Curator, Department of Geology. 


Cuicaco, U. S. A. 
October, 1913. 


NEW TRILOBITES FROM THE MAQUOKETA BEDS OF 
FAYETTE COUNTY, IOWA 


BY ARTHUR WARE SLOCOM 


The specimens upon which this paper is based represent the results 
of two visits to Fayette County, Iowa, made by the writer, one in July, 
1910, and the other in October, 1912, supplemented by specimens from 
the collection of Mr. A. G. Becker of Clermont, Iowa, and from the 
collections of the State University of Iowa. 

The Maquoketa beds constitute the uppermost deposits of the 
Ordovician system found in the state of Iowa. In a few localities they 
are overlaid, unconformably, by Niagaran limestones, but usually they 
underlie the drift. These beds have been worked out by Savage in his 
“Geology of Fayette County.”’* He divides the formation into Lower, 
Middle and Upper Maquoketa beds. The Lower member attains a 
maximum thickness of 95 feet and consists of alternating layers of 
shale and argillaceous limestone. Some of the layers are quite fos- 
siliferous. The Middle division consists of 40 to 60 feet of cherty 
limestone with few fosstls. No trilobites have been observed from 
these beds. The Upper division has a thickness in some places of 
125 feet. It is composed of a plastic blue-gray shale. In the upper 
portion occurs a zone 8 to 12 feet in thickness, in which are thin cal- 
careous layers composed almost entirely of fossil shells. Below this 


. zone the shale is practically barren of fossils, but contains numerous 


crystals of selenite. The lithological characters of the various divisions 
of the Maquoketa beds are quite constant at the various Ses 
studied. 

The Maquoketa beds of Pavetes County afford a fauna of unusual 
interest both as to the number of species represented and the excel- 
lent state of preservation of the specimens. Other localities afford a 
greater number of individuals, but few, if any, excel it in the quality of 
the material. SavageT reports 68 species divided as follows: Sponges 
2, Corals 2, Brachiopods 31, Pelecypods 4, Gastropods 11, Pteropods 2, 
Cephalopods 7, and Trilobites 9. 

In the material collected and identified by the writer, the number 
of species obtained in the various groups agrees practically with the 


_ above list with the exception of the trilobites. Of these twenty species 


*Iowa Geological Survey, 1904, Vol. XV, pp. 433-546. 
fLoc. cit., p. 486. 


43 


44 Frerp Museum or Naturat History—Geo.ocy, Vor. IV. 


were determined. A number of species of crinoids and cystoids, prob- 
ably six or eight species of which Savage made no mention, were also 
found. Of the twenty species of trilobites twelve were found to be new 
and are here described and figured. Five of the eight species which: 
have been previously described are here redescribed and figured. The 
remaining three species were too fragmentary to admit of description. 
Thus far the only group that has been critically studied by the 
writer is the trilobites and the finding of so many new species in that 
group would indicate that when the other groups are studied new 
material will be discovered. A beginning has been made on the echino- 
derms, and so far none of them appears to be referable to known species. 
If they prove to be new, they will probably be described in a future 


paper. : 
CLASSIFICATION AND TERMINOLOGY 


The classification here used is that prepared by Prof. Charles E. 
Beecher and given in the English edition of Zittel’s Text Book of Paleon- 
“8 tology. For definitions of the 
various orders and families the 
reader is referred to that work. 
In order to make clear in 
what sense various terms are 
used by the writer, the follow- 
ing glossary is given. The 
letters or figures in parentheses 
refer to text figure 1. 
Annulations: The ring-like — 
divisions of the axis of the 
pygidium. (13) 
Anterior: Situated in front. 
Anterior limb of the facial 
suture: The portion of the facial — 
suture lying in front of the © 
eye. (2) ; 
Axis: The median longitu- — 
dinal lobe of a trilobite. (a). — 
-Carapace: The hard shell 
covering the dorsal surface of — 
a trilobite. 
Caudal spine: A spine at — 
the posterior extremity of the — 
‘ Figure tI. Diagrammatic figure of a Trilobite. pygidium. (z 2) 


OcToBER, 1913. NEw TRILOBITES — SLocoM 45 


Cephalon: The head of a trilobite. (C) 

Cheeks: The two lateral portions of the head or céphalon of a trilo- 
bite, divided into fixed (7) and free (5) cheeks by a facial suture. 

Compound eyes: Eyes commonly present upon the free cheeks of 
trilobites; they are made up.of a large number of small facets. (4) 

Cranidium: The portion of the head or cephalon of a trilobite lying 
between the facial sutures, comprising the glabella and the fixed cheeks. 

Distal: Away from the median line. 

Dorsal: Pertaining to the back. 

Dorsal furrows: The furrows or depressions bounding the axial or 
medial longitudinal lobe of a trilobite; same as the axial furrows. (d) 

Doublure: The infolded margin of the trilobite test. 

Facial suture: The suture in the head or cephalon of a trilobite 
separating the fixed from the free cheeks. (2, 6) 

Fixed cheek:. The portion of the cephalon or head of a trilobite 
lying between the glabella and the facial suture. (7) 

Free cheek: Lateral portion of the cephalon or head of a trilobite, 
lying between the facial suture and the lateral cephalic border. (5) 

Frontal lobe: That portion of the glabella anterior to the first lateral 
furrows. (19) 

Genal angles: The postero-lateral gaules of the cephalon or head of 
a trilobite. 

Genal spines: The posterior prolongation into spines of the genal 
angles of a trilobite. (9) 

Glabella: The central or axial portion of the cephalon or head of a 
trilobite. (g) 

Holochroal eyes: Compound eyes of a trilobite whose visual area is 
covered with a continuous horny integument. 

Hypostoma: The under lip of a trilobite. 

Lateral furrows: The transverse furrows or grooves of the trilobite 
glabella, sometimes continuous across the glabella and sometimes 
greatly modified. (1) These furrows define the lobes of the glabella. 
(17) 

Marginal border: The thickened or otherwise differentiated external 
border of the cephalon and pygidium of a trilobite. (15) 

Marginal furrow: The groove or depression lying just within the 
marginal border of the cephalon and pygidium of a trilobite. (8) 

Occipital furrow: The posterior transverse groove or furrow of the 
glabella of a trilobite, lying in front of the occipital segment. (16) 

Occipital lobes: Small, lateral lobes of the occipital segment present 
in some trilobites, which are morphologically different from the lateral 
lobe of the glabella. ° 


46 Fretp Museum or Naturat History — Geotocy, Vor. IV. 


Occipital or neck segment: The posterior transverse segment of the 
trilobite glabella, lying between the posterior margin and the occipital 
furrow. (3) 

Ocular ridges: Ridges extending from near the anterior extremity of 
the glabella to the eyes in some trilobites. The eye lines. 

Palpebral lobes: Lobes of the fixed cheeks within the margins of 
the eyes. The eye lobes. (18) 

Pleure: The two lateral longitudinal lobes of a trilobite, applied 
chiefly to the thoracic region and the pygidium. (p) 

. Pleural grooves: Grooves on the pleurz of the thoracic segments. 
(14) 

Pleural ribs: The fused segments in the lateral lobes of the pygidium. 
(10) : 

-Post-axial region: The flattened area occupying the median portion 
of the pygidium of some trilobites, posterior to the elevated axis. (11) 

Post-cephalic margin: The posterior margin of the head or cephalon. 

Posterior cheek furrow: The marginal furrows or grooves present in 
some trilobites, which extend across the cheeks from the extremities of 
the occipital furrow of the glabella towards the genal angles. (8) 

Posterior limb of facial suture: That portion of the facial suture 
extending from the posterior extremity of the eye to the posterior or 
lateral margin of the cephalon. (6) 

Proximal: Toward the median line. 

Punctate: Having minute depressions or pits. 

Pustulose: Covered with pustules or blister-like prominences. 

Pygidium: The tail or posterior region of the trilobite test. (P) 

Schizochroal eyes: Compound eyes of the trilobites in which the 
visual area is occupied by small openings for the separate facets. 

Segments: The transverse divisions of the thorax or pygidium. 

Test: The hard outer covering of the trilobite. 

Thorax: The central segmented region of the body of trilobites. 
(T) 


Ventral: Pertaining to the under surface. 


eS ee ae 


OctToBER, 1913. NEw TRILOBITES — SLOcoM 47 


DESCRIPTION OF GENERA AND SPECIES. 
Order OPISTHOPARIA. 
Family ASAPHIDAt, Emmrich 
Genus ISOTELUS DeKay 1824. 


Cephalic and caudal shields of nearly equal size with broad infolded 
margins; glabella nearly smooth, not lobed; free cheeks large, sometimes 
meeting in front of the cranidium; eves prominent holochroal; hypos- 
toma deeply forked; thoracic axis wide; pygidium obscurely lobed, 
segmentation often obsolete at maturity. This genus is distinguished 
from Asaphus by the absence of the lobation of the glabella, the distinct 
segmentation of the pygidial axis and the wider thoracic axis. 


IsoTELUS GIGAS DeKay. 
I. gigas DeKay, 1824. Ann. Lyceum Nat. Hist. N. Y., Vol. I, p. 
174, pl. 12, fig. 1, pl. 13, fig. 1. 

I. gigas Clarke, 1897. Pal. Minn. Vol. III, pt. 2, p. 7o1 and 706. 

A portion of a pygidium from the Lower Maquoketa at Clermont 
and one from the Upper Maquoketa at Patterson’s Springs, on account 
of their size are doubtfully referred to this species. These are the 
representation of this species from Fayette County in the Museum 
collection. The State University of Iowa has in its collection a nearly 
complete individual of this species from the Maquoketa of Florence- 
ville, Howard Co., Iowa, so that the species may be looked for in 
Fayette County. 


IsoTELUS MAxIMUS Locke. 


I. maximus Locke, 1838. Sec. Ann. Rept., Geol. Surv., Ohio, p. 246, 
figs. 8, 9. 

I. megistos Locke, 1841. Trans. Am. Geol. and Nat., p. 221. 

I. maximus Clarke, 1897. Pal. Minn. Vol. III, pt. 2, p. 7or 

and 706. : : 

This species is represented in the Museum collections by one cephalon 
in which the specific characters are well shown and several pygidia which 
probably belong to the species. They were found near the top of the 
Lower Maquoketa beds at Clermont. Most of the specimens of 


' Isotelus from this locality which have been referred by other authors to 


I. maximus are here referred to J. iowensis Owen. (See remarks under 
that species.) _ 


48 Fretp Museum or Naturat History — Geotoey, Vor. IV. 


IsOTELUS IOWENSIS Owen. -Plate XIII, figs. 1-2. 
I. iowensis Owen, 1852. Rept. Geol. Surv. Wis., Ia. and Minn., p. 
577, pl. Ila, figs. 1-7. 

“The general form and contour of the cephalic shield closely re- 
semble that of J. gigas DeKay; but the facial sutures do not converge in 
front to form a distinct angle, but describe three parts of a circle as in 
Asaphus expansus. The eyes are reticulated and the middle lobe of the 
caudal shield is defined (though sometimes somewhat indistinctly), but 
‘the segments are only obscurely pronounced. The glabella is but 
obscurely defined, and the genal angles are produced into spines. The 
thorax consists of eight segments. . 

From J. megistos, it differs in the eyes being set closer together; in 
the spines being longer, extending as low as the caudal shield; the 
pygidium more regularly elliptical, and its axial lobe more distinctly 
defined. 

From the bituminous limestone mouth of Otter Creek, Turkey 
River, Iowa.” ao 

The original description, of which the above is practically a copy, 
is so incomplete that it seems advisable to redescribe the species in more 
detail. 

Body subelliptical, length about twice the greatest breadth, moder- 
ately convex, trilobation not well developed. Entire surface finely 
punctate, the puncte being larger and more pronounced on the free 
cheeks and less conspicuous on the marginal borders than on other 
parts of the test. ete 

Cephalon semi-oval in outline, marginal border defined by a mar- 
ginal furrow which originates on the genal spines. as an angular groove 
and develops into a shallow concave furrow gradually widening to the 
front of the glabella. Dorsal furrows shallow, converging toward the 
median line in passing the palpebral lobes, then diverging to about 
their original distance apart. Cranidium moderately convex, greatest 
convexity just in front of the eyes, concave where the marginal furrow 
crosses it. The anterior margin of the cranidium forms the margin of 
the cephalon. Fixed cheeks very small, not well defined. Free cheeks 
large, with long genal spines, convex near the eyes, not produced in 
front of the glabella. The facial sutures originate on the posterior 
margin of the cephalon about midway between the dorsal furrows and 
the lateral margins, from whence they converge forward in a sigmoid 


curve to the crest of the eye lobes, which they follow, thence forward | — 


and outward in an arcuate curve, meeting the anterior margin of the 
cephalon in front of the anterior angles of the eyes; here the sutures 
bifurcate, one fork following the anterior margin until it meets the 


eee ee ee eee 


=. Te ees ee Re a 


-OcTOBER, 1913. New TRILOBITES — SLocom 49 


fork from the other side in a continuous curve or slight angulation, 
never in a distinct angle; the other fork passes over the margin and 
curves across the doublure to the base of the hypostoma. (Pl. XIII, 
fig. 2.) Hypostoma forked posteriorly, only slightly constricted at the 
base, greatest width about three-fifths the length. Compared with 
I. gigas the forks point more directly backward making the notch 
between them narrower. Eyes lunate, prominent, situated less than 
their own length in front of the posterior margin of the cephalon, rather 
near together for the genus. A rather indistinct posterior cheek fur- 
row extends across the fixed cheeks. Occipital ring and furrow obsolete. 

Thorax composed of eight segments. Dorsal furrows shallow, ill- 
defined; axial lobes depressed convex, not tapering, occupying more © 
than one-third but less than one-half the width of the thorax; pleural 
lobes curving gently upward from the dorsal furrows, then more abruptly 
downward to the lateral margins; each segment arching gently forward 
on the axial lobe, and curving slightly backward towards the extremities 
of the pleuree. A shallow concave furrow crosses the axial lobe, originat- 
ing on the posterior margins at the dorsal furrows. A more pronounced 
subangular furrow originates on the anterior margin of each pleura at 
the dorsal furrows and passes diagonally outward and backward about 
three-quarters the length of the pleura. The distal portion of each 
pleura is distinctly flattened anteriorly. The flattening occupies nearly 
the entire width at the rounded extremity of the pleura but gradually 
narrows towards the dorsal furrow until it disappears. 

Pygidium slightly narrower and longer than the cephalon, rather 
more convex, with a marginal border of uniform width. Axial lobe 
tapers abruptly near its anterior margin thereafter only moderately to 
its prominent, rounded termination, no annulations visible. The seg- 
mentation of the pleural lobes is obscure although three or four segments 
may be distinguished on young individuals. All markings are more 
distinct on young than on older individuals. 

Measurements. The figured specimen (Mus. No. P 11241) (Pl. 
XIII, fig. 1) measures: Cephalon 36.5 mm. long, 63.5 mm. wide, 
thorax 33 mm. long. Another (Mus. No. P 6969) measures: Cephalon 
21 mm. long, 36 mm. wide, thorax 18.5 mm. long, 36 mm. wide. Pygi- 
dium 24.4 mm. long, 34 mm. wide, entire length 63.9 mm. 

Remarks.— Specimens of this species have been usually referred 
to I. maximus Locke, but the writer is convinced that they belong to 
Owen’s species as the Museum collection contains one nearly complete 
individual and quantities of less complete ones that were collected at 
the type locality which agree with Owen’s description. The character 
which most easily distinguishes I. iowensis from I. maximus is the 


50 Fretp Museum or Natura. History — Geotoey, Vot. IV. 


position of the facial sutures. In J. iowensis they follow the anterior 
margin of the cephalon and unite in a curve or indistinct angle. In 
I. maximus the suture’$ run subparallel to the anterior margin and meet 
in a distinct angle so that the free cheeks are produced in front of the 
glabella, while in J. iowensis the cheeks terminate in front of the eyes. 
Owen describes the genal spines as extending the entire length of the 
thorax, but his original figures show the spines much shorter. In the 
specimens before the writer the length of the spines seems to be a 
variable character. 

Locality and horizon.— ‘‘Isotelus Zone” near the base of the Lower 
Maquoketa beds near where Otter Creek empties into Turkey River at 
- Elgin, Iowa, and at Clermont, Iowa. 


Genus MEGALASPIS Angelin 1878. 


Cephalon having its anterior portion large and flattened. Glabella 
short, more or less prominent, in front of which the facial sutures unite, 
usually, in a long drawn out point. Doublure of the cephalon divided 
by a median suture. Hypostoma arched, not forked, emarginate or 
drawn out in a point posteriorly. Thoracic axis small, pleurze rounded 
at the ends. Pleurz of the pygidium grooved, doublure of the pygidium 
narrow with a channel-like excavation. Range Ordovician, Europe and 
North America. 

This generic description is adapted from Schmidt’s* discussion of the 
Asaphidze. Beechert makes the presence of a well-defined, cylindrical 
glabella the distinguishing feature of the genus, but a study of the 
various European species discloses the fact that the form and definition 
of the glabella are variable characters. 


MEGALASPIS BECKERI{ sp. nov. Plate XIV, Fig. 5. 


Type specimen in the collection of Mr. A. G. Becker. 

General outline of the test subelliptical with its anterior margin 
produced into a long acuminate process, trilobation only moderately 
well developed. Entire surface appears smooth to the unaided eye, 
but under a lens, minute, rounded pustules are visible scattered over 
the surface. These pustules are larger and nearer together in the axial 
region, especially just in front of the glabella. 

Cephalon subtriangular in outline, with all sides of the triangle 


concave, marginal border narrow and not well defined. The posterior — 


portion of the cephalon is convex, the anterior portion flattened and 


*Rev. Ostbaltischen Sil. Trilobiten Abt. V, lief. 1 and 4. 
{Zittel-Eastman Text Book Pal:, p. 630 


{This name was proposed by Mr. E. O. Ulrich and the figure is from a photo- 
graph furnished by him. 


. 
eae eae ey. ee ee 


er 


eerie 


Sk a ee Te eae 


OcTOBER, 1913. New TRILOBITES — SLOCOM 51 


produced into a long acuminate process pointing obliquely upward. 
Dorsal furrows visible only in the occipital region. Glabella not 
defined laterally or anteriorly, depressed convex, greater elevation at 
its posterior margin, which is the greatest elevation of the entire test. 
Fixed cheeks not defined. Free cheeks large, widest near the eyes, 
where they slope abruptly to the lateral margins; the genal angles are 
produced into short spines, extending directly backward as far as the 
sixth thoracic segment; the anterior portions narrow gradually forward 
until they meet at the anterior margin. The facial sutures originate on 
the posterior margin of the cephalon about midway between the dorsal 
furrows and the genal angles, converging slightly to the eyes; in front of 
the eyes they converge more rapidly, extending subparallel to the 
antero-lateral margins of the: cephalon and meeting in front of the 
glabella. The palpebral lobes are prominent, their proximal edges 
being produced towards the median line of the glabella and interrupting 
the dorsal furrows; the transverse ridges thus formed appear to be > 
comparable to lateral glabella lobes rather than ocular ridges. Form 
of the eyes not known, but one of the palpebral lobes on a cranidium 
(Mus. No. P 16998) indicates that they were elevated similar to those 
of Nileus vigilans. Occipital segment and furrow obsolete. Shallow 
posterior cheek furrows extend laterally from the dorsal furrows, meet- 
ing the lateral furrows near the genal angles. 

Thorax composed of eight segments. Dorsal furrows shallow; axis 
depressed convex, slightly tapering posteriorly; occupying somewhat 
more than one-third the width of the thorax; no transverse furrows; 
the pleurz curve outward and then abruptly downward to the lateral 
margins; distal extremities rounded; angular furrows originate at the 
dorsal furrows and cross the pleure diagonally. 

Pygidium slightly narrower and much shorter than the cephalon, 
marginal border defined only near the posterior margin: Axis tapering 
to a prominent rounded termination well within the margin. The 
pleural lobes curve abruptly to the lateral margins. The segmentation 
of the pygidium is not visible on the outer surface of the test, but on its 
inner surface some traces may be found on both axis and pleure. 

The measurements of the type specimen are as follows: Length 
over all 89.1 mm.; width at genal angles 37.2 mm.; length of the cephalon 
on median line 42.5 mm.; length of cephalon including genal angles 57 
mm.; length of thorax 21.3 mm.; width of thorax at anterior segment 
33 mm.; length of pygidium 26.5 mm.; width of pygidium at anterior 
margin 29.5 mm. 

So far as known to the writer, only two American species have been 
referred to this genus. These are M. ? gonioceras Meek from the 


52 Frerp Museum or Naturat History — Greotocy, Vot. IV. 


Quebec group of Utah and M. belemnura White from a similar horizon 
in Nevada. These species were described from pygidia only, so that 
their reference is somewhat doubtful. Judging from the: descriptions 
and figures of the above species, neither of them closely resembles the 
pygidium of M. beckeri; so that comparison must be made with European 
species. In general form M. beckeri most closely resembles M. ex- 
tenuata Angelin from Gothland, Sweden, but is distinguished from that 
species by not having the glabella defined laterally or anteriorly, by 
having its genal spines less flaring and by having much narrower mar- 
ginal borders of the pygidium. 

The specific name is given in honor of Mr. A. G. Becker, whose 
collection contains the type specimen. 

Localities and horizon.— The species is known to the writer by a- 
practically complete specimen, the type, and a nearly complete cra- 
nidium (Mus. No. P 16998). The type is from the Lower Maquoketa 
‘beds at Clermont and the cranidium from a similar horizon at Post- 
ville Junction, Iowa. 


Genus NILEUS Dalman 1826. 


“Corpus breve, convexum leve, sulcis dorsalibus longitudinalibus nullis; 
segmentis trunci 8. Oculi maximi, laterales.” (Paleden oder die Soge- 
nannten Trilobiten, p. 70.) 

The above is Dalman’s original description of the genus and may be 
somewhat elaborated as follows: Body elliptical, convex, smooth. 
Cephalon twice.as wide as long, convex, genal angles broadly rounded. 
Glabella undefined laterally, no lateral furrows. The facial sutures 
originate on the posterior margin of the cephalon, curve forward to the 
eye lobes, over which they pass, thence with a sigmoid curve to the 
anterior margin, where they meet. Eyes large, lunate, holochroal. 
Rounded hypostoma with elevated border. Eight thoracic segments, 
indistinctly tri-lobed, axial lobe the broader. Pygidium twice as broad 
as long, neither lobed nor segmented, broadly rounded posteriorly. 
Range, Ordovician of Europe and North America. 


NiILeus vicILrAns Meek and Worthen Plate XIV, Figs. 9-15. 


Asaphus vigilans M. & W., Geol. Surv. Ills., Vol. VI, p. 497, pl. 23, 
fig. 6. 
Nileus vigilans Clarke, Pal. Minn., Vol. III, pt. 2, p. 712, figs. 17-19. 
Body convex, trilobation very obscure, subelliptical in outline, 
lateral margins nearly parallel. Surface smooth to the naked eye, but. 
under a magnifier the extremities are ornamented with transverse 


a 


OcTOBER, 1913. New TRILoBITES — SLocom (ee 


impressed lines. These lines are most distinct on the doublure and 
anterior portion of the glabella and rather indistinct on the pygidium. 
Free cheeks finely punctate. 
: Cephalon sublunate in outline, somewhat depressed on the antero- 
lateral margin, convex, frontal slope inflated but not projecting. Mar- 
gin marked by a slight recurved elevation; genal angles obtusely 
rounded; free cheeks large, produced in front of the cranidium nearly or 
quite to the median line. Eyes small for the genus but prominent, 
situated at points each one-third the transverse diameter of the cephalon, 
and about their own diameter from the posterior margin. The facial 
sutures originate on the posterior margin of the cephalon at about one- 
third the distance from the dorsal furrows to the genal angles, curve 
obliquely forward over the palpebral lobes thence in sigmoid curves to 
the anterior margin, where they meet. Glabella furrows, dorsal furrows 
and occipital ring and furrow are obsolete on the surface of the test, but 
on casts the location of the dorsal furrows is indicated on each side by 
pits at the posterior margin of the cephalon. These pits are connected 
by a shallow occipital furrow, running parallel to the posterior margin 
until near the median point, where it arches forward. 

Thorax composed of eight broad, flat segments, trilobation very 
obscure; axis about three-fourths the entire width, depressed convex; 
pleural lobes curving regularly to the lateral margins; segments arched 
slightly forward on the axial lobe, somewhat curved backward. On 
enrolled specimens this backward curve appears greater than it really is 
on account of the flattening of the anterior portion of the pleuree, which 
originates at the dorsal furrows and gradually widens distally. On the 
anterior border at the dorsal furrow of each segment are small projec- 
tions which point forward and fit into. corresponding notches of the 
preceding segment. The segments are without grooves on the test, but 
on the casts a shallow groove connects the dorsal furrows. 

Pygidium somewhat narrower but longer than the cephalon, de- 
pressed convex, sloping equally to the margins, trilobation and seg- 
mentation wanting on the surface of the test but faintly discernible on 
the casts. 

_ Remarks.— The Maquoketa specimens, above described, appear to 
correspond in practically all points to the original description and are 
from a similar horizon to the type. The Galena and Trenton speci-_ 
mens referred to this species and described by Clarke appear to differ as 

follows: The facial sutures reach the margin of the cephalon in front of 
the eyes, while in the Maquoketa specimens the sutures reach the 
anterior margin near the median line of the cephalon. The front part . 
of the cranidium is more inflated in the Maquoketa specimens. 


54 Frerp Museum or Natura History — Grotocy, Vor. IV. 


Locality and horizon.— This species was originally described from 
the Cincinnati shales of Carroll and Kendall Counties, Illinois. It has 
been collected by the writer from the Lower Maquoketa beds at Cler- 
mont, Elgin, and Bloomfield, Iowa, and Upper Maquoketa bed at 
Patterson’s Springs near Brainard, Iowa. 


Genus BUMASTUS Murchison 1839. 


“General characters.— Pars anterior; capitis rotundato-convexa, 
subequalis; oculis lunatis, glabris, remotis. Pars costalis s. corpus, sulcis 
longitudinalibus vix apparentibus, costis decem. Pars posterior maxima, 
rotundato-tumida, equalis. Omnes teste partes ultro citroque, linearum 
sulcatarum subtilisimis ambagibus punctulisque confertis, insignite.”’ 
Silurian System 1839, p. 656. 


(TRANSLATION) 


Generic characters.— Anterior part; (cephalon) rotund, convexity 
of the head subuniform; eyes lunate, smooth, situated far apart. Seg- 
mented part of the body; (thorax) longitudinal furrows scarcely dis- 
cernible, ten segments. Posterior part (pygidium) large, roundly, 
uniformly tumid. All parts of the test irregularly marked by impressed 
lines, interspaces finely and obscurely punctate. 

The above is the original description of the genus. The author 
states later that the surface markings may be of only specific importance 
and that he has added them to the generic definition provisionally. 


BUMASTUS BECKERI sp. nov. Plate XIV, Figs. 1-4. 

Type specimens: holotype in collection of Mr. A. G. Becker, one 
paratype in collection of State University of Iowa, and the other 
No. P 16708 Field Museum. 

Description.— Body oblong, slightly ovate, width at the genal 
angles about half the entire length. Dorsal furrows nearly obsolete on 
the cephalon and thorax and entirely so on the pygidium. Surface, 
except in the region of the palpebral lobes, dorsal furrows and the 
anterior central portion of the glabella, marked with indented, trans- 
verse lines, more or less parallel to each other and to the transverse 
divisions of the test. These lines are conspicuous and close together on 
the doublure, somewhat less so on the cephalon and anterior segments 
of the thorax. On the posterior segments and pygidium they are in- | 
conspicuous and only discernible with a magnifier. 

Cephalon strongly convex, semicircular in outline; the location of 
the dorsal furrows indicated by two almost imperceptible grooves 


OcTOBER, 1913. NEw TRILOBITES — SLOcOoM 55 


leading up to longitudinally elongate depressions situated just in front 
of a line joining the anterior edges of the eyes and somewhat nearer to 
the eyes than to the median line of the cephalon. These depressions 
appear as sublunate grooves on the casts, but on the surface of the test 
only as a slight flattening. The regular curvature of the cephalon, 
aside from the flattening just referred to, is interrupted only by the 
palpebral lobes. Eyes far apart, situated at about half their length 
from the posterior margin of the cephalon. Facial sutures originate on 
the posterior margin of the cephalon on a level with the lower edges of 
the eyes, from whence they pass forward and upward around the eyes, 
thence obliquely downward to the antero-lateral margin of the ceph- 
alon. Free cheeks small, genal angles obtusely rounded. Occipital 
ring not discernible on either test or cast. 

Thorax composed of ten segments, smooth and flat, gradually 
narrowing to the almost obsolete dorsal furrows, at which points they 
bend backward and downward to the lateral margins; the axis occupies 
about two-thirds of the width of the thorax; eet furrows appear on 
the casts as two parallel grooves. 

Pygidium strongly arched, transversely oval, Rac about two- 
thirds the width, no trace of the dorsal furrows. 

Five specimens were used by the writer in making this description. 
The holotype (Pl. XIV, fig. 1) is an enrolled specimen having a portion 
of the front of the cranidium missing. It is in the private collection of 
Mr. A. G. Becker. A paratype (Pl. XIV, figs. 2-3) consists of a com- 
plete cephalon attached to nine complete thoracic segments and a 
portion of the tenth. This specimen was collected by Prof. Calvin and 
is a part of the geological collection of the State University of Iowa. 
The other paratype (Pl. XIV, fig. 4) is a pygidium attached to the 
seven posterior thoracic segments. It belongs to the Museum collec- 
tions (Mus. No. P 16708). Two somewhat distorted natural casts 
(Mus. No. P 16854) were also used in making this description. These 
casts were presented to the Museum by Mr. Becker. The dimensions 
of the type specimens are as follows: Holotype: Cephalon 18 mm. long, 
31.5 wide; pygidium 15 mm. long, 26.4 mm. wide; distance around the 
coiled specimen 74.5 mm. Allowing for the convexity of the cephalon 
and pygidium would make the length if unrolled about 60 mm. _ Speci- 
men from the State University of Iowa: Cephalon 19.6 mm. long, 
32.3 mm. wide and 18 mm. thick. Specimen P 16708: Pygidium 11 
mm. long, 19 mm. wide, length of pygidium and the seven posterior 
segments of the thorax 33 mm. 

Remarks.— Specimens of this species have been referred to B. 
orbicaudatus Billings by Calvin, Savage, and others in the various Iowa 


56 Frerp Museum or Narurat History — Greotocy, Vor. IV. 


reports. B. orbicaudatus was originally described* from a pygidium only 
and a complete specimen was afterwardsf{ figured by Billings. Re- 
ferring to this description and figure, it is evident that B. beckeri is quite 
distinct from B. orbicaudatus. The cephalon and pygidium are much 
longer in proportion to their width, and the dorsal furrows are much 
more distinct in B. orbicaudatus. The orbicular axis of the pygidium, 
which is the distinguishing character of B. orbicaudatus, is missing in 
B. beckeri. B. beckeri seems to be most closely related to B. billingsi 
Raymond and Narraway from the Trenton limestone of Canada, but it 
is considerably narrower in proportion to its length, the trilobation is 
much less pronounced and no mention is made in the description of 
B. billingsi of any transverse lines on the test. 

The specific name is given in honor of Mr. A. G. Becker, whose 
- collection contains the type specimen. 

Locality and horizon.— All specimens observed are from the Lower 
Maquoketa beds of Clermont. 


. Genus THALEOPS Conrad 1843. 


“Ovate, profoundly trilobed, lateral lobes wider than the middle 
lobe; buckler (cephalon) lunate, with very remote oculine tubercles, 
not reticulated; abdomen (thorax) with 1o-articulations; ribs without 
grooves and not alternated in size; outer half of lateral lobes suddenly 
depressed; post-abdomen (pygidium) without ribs or grooves and 
profoundly trilobed.” 

“This genus is remarkable for the great width of the buckler, and 
the very prominent laterally projecting smooth oculine tubercles. It 
differs from Bumastus in being profoundly lobed, and in having the side 
lobes as in Asaphus much wider than the middle lobe. From Jllenus | 
it may be distinguished by its ovate form, want of reticulated eyes, the 
width of the lateral lobes, and the profound lobes of the tail.’’ . Proc, — 
Acad. Nat. Sci. Phil., 1843, Vol. I, p. 331. 

The above is Conrad’s original description of the genus and to it | 
should be added that the free cheeks are produced laterally at the 
genal angles into blunt spines. 


THALEOPS OVATA Conrad, Plate XIV, Figs. 6-8. 
T. ovata Conrad, 1843. . Proc. Acad. Nat. Sci. Phil., Vol. I, p. 332. 
Illenus ovatus Whitfield, 1882. Geol. Wis., Vol. IV, p. 238, pl. 5, 
figs. 1-2. : 


*Can. Nat. Geol., Vol. iv, p. 379. 
{Cat. Sil. Foss, Anticosti, p. 27. 


OcTOBER, 1913. New TRILOBITES — SLocoM 57 


T. ovata Clarke,1897.. Pal. Minn., Vol. III, pt. 2, p. 716, figs. 17-19. 

Body broadly ovate, widest at the base of the cephalon, distinctly 
trilobed, length about equal to the width at the eye lobes. 

Cephalon broadly semicircular on the anterior margin, very. highly 
convex. Dorsal furrows clearly defined on the posterior third of the 
cephalon, obsolete in front. .Glabella convex between the dorsal fur- 
rows, not defined in front. Eyes small, pedunculate, extending laterally 
and horizontally.. Occipital segment and furrow very faintly marked, 
rounded backward. Free cheeks small, produced laterally at the genal 
anglesintoblunt spines. The facial sutures rise rapidly from the posterior * 
margin to the summit of the eye lobes, thence round gradually forward 
to the anterior margin, which they intersect in front of the dorsal furrows. 

Thorax wider than long, tapering, composed of ten smooth, slightly 
convex segments. Axial lobe depressed convex, narrower than the 
lateral lobes,‘segments arched forward. Pleure flat for more than half 
their width from the axis, then bent downward, segments strongly 
recurved toward their extremities. 

Pygidium nearly flat on top and curving abeneety to the margins, 
short, subquadratic. The posterior margin forms a very broad curve, 
width about twice the length. Axis prominent; narrower than the 
thoracic axis, tapering slightly and terminating bluntly in an elevated 
extremity, which is faintly bilobed; axis entirely surrounded by the 
dorsal furrows; annulations of the axis nearly obsolete. 

The surface of the cephalon is covered with epidermal niet 
except in the dorsal furrows and on the palpebral lobes. On the cheeks 
and anterior portion of the glabella the puncte are vertical and isolated, 
on the posterior surface of the glabella they are oblique and crowded. 
The surface of the thorax appears to be smooth. Doublure marked 
with prominent lines parallel to the-anterior margin. Pygidium sparsely 
punctate on the posterior margin but on the anterior portion the 
punctations are deep, coarse, and arranged in transverse rows. 

The foregoing description is based on a practically complete speci- 
men from the Platteville beds at Mineral Point, Wisconsin, in the 
paleontological collection of the University of Chicago. The Fayette 
County specimens have been compared with the Platteville specimen 
and agree so well that they must be considered to be specifically identi- 
cal, although previously J. ovata has been found only at lower geological 
horizons. 

This species is represented in the Museum collections from Fayette 
County by a nearly complete cranidium from the Lower Maquoketa at 
Clermont and another from the Upper Maquoketa at Patterson’s 


_ Springs. 


58 Fretp Museum or Naturat History — Georoey, Vor. IV. 


Family LICHADIDA, Barrande. 
Genus AMPHILICHAS Raymond 190s. 
(Platymetopus* Angelin 1854, Paralichas Reed 1902.) 


By combining the various characters enumerated in previous de- 
scriptions this genus may be described as follows: 
Cephalon broadly subtriangular, tuberculate. Anterior lobe of the 
-glabella dominating the other lobes, and continuous with the axis; a 
single pair of lateral glabella furrows opening directly into the occipital 
furrow; no third lobes; all lobes depressed convex, all furrows narrow; 
dorsal furrows concave inward; occipital ring forming a band. Pygidium 
with two rings on the axis; post-axial piece not defined posteriorly; 
three pairs of pleurz, each with pleural furrow and free point; third pair 
incompletely defined from post-axial piece, points short and blunt. 


AMPHILICHAS RHINOCEROS sp. nov. Plate XV, Figs. 5-6. 


Type specimen No. P 11181 Field Museum. 

Glabella large, occupying nearly the entire width of the cranidium, 
depressed convex posteriorly, inflated in front, subpentangular in out- 
line, rounded anteriorly, greatest width just in front of the eyes; the 
single pair of glabella furrows originates on the lateral margins, curves 
gently inward and backward for about half the length of the glabella, 
thence backward subparallel until they join the occipital furrow. 
They thus divide the glabella into a median and two lateral lobes. 
Median lobe broad in front, posterior half only slightly convex, anterior 
half abruptly inflated, length about two and one-half times the width at 
the occipital furrow. Lateral lobes undivided, margins subparallel, 
width about equal to that of the median lobe, moderately convex except 
in front where they bend outward and downward to the lateral margins; 
greatest elevation near the dorsal furrows in line with the palpebral 
lobes, where large nodes rise abruptly from the dorsal furrows but else- 
where gradually; these nodes form the bases of the two, long, lateral spines. 
The occipital segment forms a wide, depressed, transverse band, widest 
in the middle and gradually narrowing towards the dorsal furrows; 
posterior margin slightly concave, with a well developed doublure. 
Dorsal furrows, as well as glabella and occipital furrows, narrow but 
well defined. Fixed cheeks. small, depressed, convex, aside from the 
* palpebral lobes, which rise abruptly; the only portion of the palpebral 
*Platymetopus Angelin, 1854, preoccupied by Dejean, 1829, for genus of Coleop- 


tera. Paralichas Reed, 1902, suggested in its place, preoccupied by White, 1859, 
also for Coleoptera. 


ee a ee ee a ee 


ie 


ee 
eR a so 5 


OcTOBER, 1913. NEw TRILOBITES — SLOCOM 59 


lobes observed is that attached to the fixed cheek. This is elevated, 
lunate in form with the convex side toward the dorsal furrows. The 
marginal border of the cephalon is represented only by a single some- 
what crushed fragment, but this fragment indicates that there was 
a narrow marginal border similar to that of A. bicornis Ulrich. Eyes 
and free cheeks not preserved. Surface of the cephalon finely papil- 
lose, with tubercles of various sizes more or less regularly arranged 
thereon. Two of the larger of these tubercles occur along the median 
line of the glabella, one on each lateral lobe, and three form a transverse 
row on the occipital segment; aside from these tubercles, the inflated 
anterior portion of the glabella supports a pair of recurved hornlike 
processes, 2.5 mm. in diameter and 29 mm. long (measured on the outer 
side of the curve); these processes diverge somewhat and curve upward, ~ 
then backward. Another pair of processes of about the same size 
occurs; one on each lateral lobe of the glabella, near the dorsal furrow, 
in line with the eyes. Exact length of the lateral pair of processes not 
known. 

Thorax and pygidium unknown. 

The specimen (Mus. No. P 11181) on which the above description is 
based consists of a nearly complete cranidium of which the inner sur- 
face of the test is exposed with one of the anterior horns complete and 
in natural position and one of the lateral ones bent outward with the 
end missing. The dimensions are as follows: Length of cranidium, 
along the median line, 32 mm.; greatest width of glabella (in front of 
eyes) 42 mm.; width of median glabella lobe on anterior margin 18 mm.; 
width at occipital furrow 11.5 mm.; width of lateral lobes 11.5 mm.; 
width of occipital segment on median line 7 mm.; width at dorsal 
furrows 5.5 mm. 

Remarks.— In general form and proportion the cranidium above 
described approaches A. bicornis Ulrich, from a similar horizon in 
Minnesota, but is distinguished from that species by the number and 
position of the hornlike processes as well as by the variation in size of 
the surface tubercles; also in a side view of the glabella of A. bicornis the 
outline of the surface is convex, while in A. rhinoceros the outline near 
the middle is concave, due to the inflation of the anterior portion. 

Locality and horizon.— Upper layers of the Lower Maquoketa beds 
_at Elgin, Iowa. 


AMPHILICHAS CLERMONTENSIS sp. nov. Plate XV, Fig. 7. 

Type specimen No. P 11257 Field Museum. 

Cephalon subtriangular, broadly rounded anteriorly, much shorter 
in proportion to the width than A. rhinoceros. Glabella convex, great- 


60 Fretp Museum or Naturat History — Geotocy, Vot. IV. 


est elevation just in front of the center, to which point it rises gradually 


from the posteror and lateral margins and much more abruptly ante- 
riorly; subpentangular in outline, widest in front of the eyes; a single 
pair of glabella furrows originates on the lateral margins, curves abruptly 
inward and upward, then converges backward until it meets the occipital 
furrow, forming a large median lobe and two smaller lateral lobes. 
Median lobe very broad anteriorly, more than twice the width at the 
occipital furrow. It comprises nearly two-thirds of the glabella. 
Lateral lobes undivided, margins subparallel, conforming to the general 
convexity of the glabella, abruptly bent downward anteriorly. Occipital 
segment a flat or slightly concave, transverse band, widest at the 
juncture of the occipital and glabella furrows, narrowing slightly to the 
median line and’ more so laterally. Occipital and glabella furrows nar- 
row but distinct. Surface smooth to the naked eye, but a magnifier 
shows it to be covered with variously sized pustules. No nodes or spines 
interrupt the regular curvature of the cephalon. 

Thorax and pygidium unknown. 

The specimen here described (Mus. No. P 11257) consists of an 
incomplete glabella. The cheeks and marginal border are entirely 
missing. The median lobe and one lateral lobe are nearly complete, and 
the other lateral lobe is somewhat less so. The occipital, one dorsal and 
the glabella furrows are well indicated and the median portion of the 
occipital segment is intact. While the specimen leaves much to be 
desired, yet the generic characters are well shown and the specific char- 
acters fairly well. 

The dimensions are as follows: 

Length of glabella on median line (exclusive of occipital 


TENG sor apr oe eg Fee was Ais Te 24.5 mm. 
Greatest width of glabella (in front of the eyes)......... 30 mm 
Width of glabella at occipital furrow................... 26 mm. 
Width of median glabella lobe on anterior margin, about..24 mm. 
Width of median glabella lobe on occipital furrow....... II 5mm. 
Width of lateral glabellatobés. 3. csi ka ee ek i es 8.5 mm. 
Length of lateral glabella lobes.:..........50.....200.: 17 mm, 
Width of occipital segment on median line.............. 3.5 mm. 
Width of occipital segment behind glabella furrows...... 4.2mm. 


Amphilichas clermontensis is distinguished from the other members of 
this genus by the much greater width of the glabella in proportion to its 
length and by its more nearly arcuate curvature both longitudinally and 
transversely. In surface ornamentation it resembles A. circullus from 
the Trenton, but in form it is quite distinct from that species. 

Locality and horizon.—Lower Maquoketa beds, Clermont, Iowa. 


Te ee a ee ee eee a ee 


OcTOBER, I913. New TRILOBITES — SLocom 61 


Order PROPARIA. 
Family ENCRINURIDA:, Linnarsson. 
Genus ENCRINURUS Emmrich 1844. 


“Cephalon tuberculate; glabella pyriform, prominent; free cheeks 
narrow, separated in front by a small rostral plate; eyes small, elevated 
on conical prominences; thoracic segments eleven; pygidium triangular, 
numerous annulations on the axis; pleure with few ribs.” Range, 
Ordovician and Silurian, Europe and America. (Zittel-Eastman Text 
Book Pal., p. 634.) 

Vogdes* divided the above genus by placing all species without 
- genal spines in Cryptonymus Eichwald, but his point does not appear to 
be well taken for two reasons. (1) In 1825 Eichwald described the 
genus Cryptonymus with C. scholotheimi as genotype. Seven other 
species were placed in the genus. The genotype and three others were 
found to belong to the genus Asaphus Brong., the balance to Illenus 
Dahlman. In 1840 Eichwald again used the name Cryptonymus for a 
genus entirely different from the one described, in 1825, thus using a 
preoccupied name. (2) The presence or absence of genal spines does 
not appear to the- writer to be of generic importance. 


ENCRINURUS PERNODOSUS sp. nov. Plate XVI, Figs. 5—7. 


Type specimens Nos. P 17038 and P 16930 Field Museum. 

Body ovate in outline, trilobation distinct, without genal or caudal 
spines. 

Cephalon sublunate in outline, anterior margin inflated, width more 
than twice the length. Glabella subhemispherical, width somewhat less 
than the length, slightly protruding beyond the anterior margin; three 
pairs of indistinct lateral glabella furrows define the lateral lobes; these 
furrows rapidly decrease in depth from the dorsal furrows and become 
obsolete among the tubercles; a well-defined furrow originates on the 
dorsal furrows about midway between the anterior lateral glabella 
furrows and the anterior marginal furrow and bends slightly forward in 
crossing the anterior lobe of the glabella; anterior glabella lobe large, 
comprising nearly half the glabella, lateral lobes quadrangular, de- 
creasing rapidly in size posteriorly; occipital segment narrow, resembling 
the axial portion of ‘one of the thoracic segments in size and form; 
occipital furrow narrow, angular, well-defined; dorsal furrows deep, 
angular, diverging somewhat from the occipital furrow to the anterior 

*Trans. San Diego Soc. Nat. Hist. Vol. I, No. 2, p. 74. 


62 Frerp Museum or Natura History — Geoxoey, Vor. IV. 


marginal furrow; cheeks subtriangular in outline, depressed conical in 
form, sloping gradually to the palpebral lobes; eyes small, pedunculate, 
holochroal; facial sutures originating at the genal angles, passing directly 
to the palpebral lobes, which they cross, thence obliquely forward, cross- 
ing the dorsal furrows and subparallel to the furrow crossing the gla- 
bella, until they meet the rostral plate, where they bend abruptly forward 
to the anterior margin; free cheeks large, more than twice the size of the 
fixed cheeks; marginal borders well-defined by the marginal furrows, 
those of the posterior margin narrow, those of the lateral margins wide, 
gradually narrowing to the anterior margin; genal angles rounded, ending 
in a large tubercle. Surface of the glabella covered with large rounded 
tubercles, that of the cheeks near the dorsal and lateral marginal fur- 
rows tubercular, other portions covered with elongated pits radiating 
from the eyes; surface of the occipital segment and marginal borders 
finely granulose. Hypostoma broadly elliptical, convex. 

Thorax composed of eleven segments; axis convex, about the 
same width as the pleure; tapering slightly posteriorly, pleure 
curving regularly to the lateral margins; surface of the thoracic seg- 
ments finely granulose, ornamented with indistinct nodes; these vary 
from two to four on the axis and one or two on each pleura; no pleural 
grooves. | 

Pygidium triangular, convex, width somewhat ‘greater than the 
length, rounded posteriorly, no caudal spines. Axis convex, conical, 
occupying about one-third the anterior margin of the pygidium, with 
many annulations, which diminish in size and distinctness posteriorly so 
that the number visible depends to a great extent on the amount of 
abrasion to which the specimen has been subjected; most of the annula- 
tions bear two to four rounded nodes, having decided pits in their 
apices. Pleuree composed of seven distinct ribs, which curve slightly 
upward and then downward and backward to the margins; each rib 
ornamented with two or more rather indistinct nodes near the dorsal 
furrows and with a prominent knoblike distal end. 

Dimensions of the type specimen: 


AHOLD OF DERAHI oooeeey hadh es Sie Ge ee Fe bay oe On Io mm. 
Width of cephalon at genal angles...................4. 17.5 mm. 
Length of glabella exclusive of occipital segment......... 8.4 mm. 
Width of glabella on anterior margin................... 8.0 mm. 
Width of glabella on occipital furrow................... 5.0mm. 
Entire length of body measured on a coiled specimen.... 32.0 mm. 
Length of pygidium (Mus. No. P 16930)............... 8.2 mm. 
Wicktls of Wey rte eee a a de bone sic wa we Rees 9.6 mm. 
Width of axis at anterior margin........... Bunuats ey atthe 3.6 mm. 


OcTOBER, I913. New TRILOBITES — SLOcoM & 63 


The species is known from the holotype (Mus. No. P 17038) in which 
the cephalon, about two-thirds of the thorax and most of the pygidium 
are preserved, from five detached pygidia and from one specimen in 
which the entire pygidium is attached to all but the anterior segment, of 
the thorax. 

In general form and proportions the species here described resembles 
E. variolans, Brongniart from the Wenlock Limestone of England, but 
the tubercles are much larger, the transverse furrow on the glabella is 
missing and the annulations of the pygidia are fewer in number. E. 
sexcostatus Salter possesses the transverse furrow, but that seems to be 
about the only resemblance with this species. 

Locality and horizon.— The holotype is from the top of the Lower 
Maquoketa beds at Bloomfield. The species has been found at a 
similar horizon at Clermont and Elgin, and at a somewhat lower 
horizon at Clermont. 


Genus CYBELOIDES gen. nov. 


Body distinctly trilobate, outline, aside from the spines, sub-ovate. 
‘Cephalon sub-lunate; genal angles produced-into spines. Glabella 
divided by two longitudinal furrows into a central and two lateral lobes; 
the lateral glabella furrows are indicated by three pits situated in each 
longitudinal furrow. Eyes small, pedunculate; the facial sutures 
originate on the lateral margins somewhat in front of the genal angles. 
Thorax consists of twelve segments; the five anterior segments are 
faceted at their distal extremities. The sixth segment, and in some 
specimens the sixth to the twelfth, is abruptly bent backward at the 
lateral margin of the thorax and produced into long spines. Pygidium 
small, axis conical with many annulations, pleural lobes with few ribs. 

Genotype, Cybeloides iowensis. Range, Ordovician of North 
America. 

This genus differs from Cybele Loven as exhibited in C. bellatula, 
the genotype, in the form of the glabella furrows and in the genal angles 
being produced into spines instead of being rounded. 

Four American species have been referred to the genus Cybele; C. ella 
Narraway and Raymond, C. prima (including C. valcourensis) Ray- 
mond, C. winchelli Clarke, and a portion of a pygidium referred to the 
genus without specific determination by Ruedemann. Of the first two 
only is the form of the glabella known, but both of these agree with 
C. iowensis here described. Narraway and Raymond called attention to 
the difference of the form of the glabella of this species from that of the 
European species, but still referred their species to Cybele. While the 


64 Frerp Museum or Naturat History — Geotocy, Vor. IV. 


presence or absence of genal spines would not be of generic importance, 
the fact that the glabella is divided longitudinally into three lobes 
appears to be ample reason for separating the American from the 
European species generically. This is the character which distin- 
guishes Chasmops from Dalmanites and the various genera of the 
Lichadz are based on the variations of the glabella furrows. 

Of the eleven European species of Cybele known to the writer, two 
have only the pygidium described or figured; the other nine all have 
well-marked lateral glabella furro vs. Three of these species described 
by Schmitz, viz., C. grewingki, C. kutorge and C. revaliensis, exhibit a 
tendency toward the American forms. The lateral furrows are sep- 
arated from the dorsal furrows by a narrow lateral margin of the gla- 
bella, but there are no traces of longitudinal glabella furrows. 

The bibliography of the genus is as follows: 

Cybeloides ella Narraway and Raymond. 

1906 Cybele ella N. & R., Ann. Carnegie Mus., Vol. 3, No. 4, p 
 -so8, fig. 1. Black River, Ottawa, Canada. 

Cybeloidesiowensis Slocom, genotypethispaper. Lower Maquoketa, 
Iowa. © 

Cybeloides prima Raymond. : 

1905 Glaphurus primus Raymond, Ann. Carnegie Mus., Vol. 3, 
No. 2, p. 362, pl. 14, figs. 7-8. 
1905 Cybele valwurensle Raymond, ibid p. 362, pl. 14, fig. 9. 
1906 Cybele prima Narraway and Raymond, Ann. Carnegie Mus., 
; Vol 3, No. 4, p. 601. Chazy, N. Y. 

Cybeloides ? winchelli Clarke. 

1897 Cybele winchelli Clarke, Pal. Minn., Vol. 3s pt. 2, p. 742, 
fig. 59. Galena Limestone, fear: 

Cybeloides ? sp. ? Ruedemann. 

~ rg01 Cybele sp. ? Ruedemann, N. Y. St. Mus. Bull. 40, p. 66, pl. 
4, fig. 12. Trenton, N. Y. . 

The last two species are placed in the genus provisionally until the 

characters of the glabella are known. 


CYBELOIDES IOWENSIS sp. nov. Plate XVI, Figs. 1-4. 


Type specimens. Nos. P 16631, 16633 and 17039 Field Museum. 

Body depressed convex, distinctly trilobed, outline, aside from the 
spines, subovate, tapering rather rapidly to a small pygidium. Surface 
finely granular with many more or less prominent rounded nodes. 

Cephalon short, width nearly three times the length, outline sub- 
lunate with the anterior. lateral margins inflated. Glabella convex, 
inflated anteriorly, somewhat longer than wide, widest across the 


OcTOBER, 1913. NEw TRILOBITES — SLocoM 65 


lateral lobes; median lobe clavate, narrow at the occipital furrow, 
gradually widening for about half its length then abruptly widening 
until its greatest width is reached, rounded in front; lateral lobes 
longitudinally oval; longitudinal glabella furrows originating in deep 
pits on the occipital furrow, converging slightly, then curving forward 
and outward; the positions of the lateral glabella furrows are indicated 
by three pits in the longitudinal furrows; occipital ring prominent, more 
elevated than any other part of the cephalon, wide between the glabella 
furrows, abruptly narrowing towards the dorsal furrows, bearing a large 
median node with a smaller one on each side of it; occipital furrow shal- 
low and ill-defined in the median portion, deepened into pits near the 
dorsal furrows. Surface of the glabella finely granular with many 
prominent rounded nodes arranged in more or less uniform transverse 
rows; the two largest nodes are close together near the anterior margin 
and point forward. On the median line of the glabella just in front of a 
line connecting the anterior pair of glabella pits is a circular, well-_ 
marked pit. Cheeks large, depressed convex, not rising as high as the 
glabella, genal angles produced into long spines, which extend backward 
more than half the length of the thorax. Marginal borders convex; . 
posterior marginal furrows narrow and deep, lateral marginal furrows 
not well-defined. The facial sutures originate on the lateral margin 
just in front of the genal angles, pass almost straight to the palpebral 
lobes, after crossing which they extend forward for a short distance, then 
curve abruptly toward the median line and again forward to the ante- 
rior margin. Eyes small, pedunculate and very prominent (Pl. XVI, 
fig. 4), situated on a line with the anterior pair of glabella pits near the 
dorsal furrows; a pair of ocular ridges connects the eyes with the anterior 
lobe of the glabella. Surface of the cheeks inside the marginal borders 
reticulated, or covered with rows of pits; surface of the marginal borders 
granular like the glabella, many nodes irregularly distributed over the 
cheeks; these nodes average somewhat larger than those on the glabella; 
‘the larger ones are on the posterior panei and point backward instead 
of outward. 

Thorax composed of twelve segments, rather rapidly tapering . 
posteriorly, distinctly trilobed; axis convex, less than one-third the 
width of the thorax; the pleural lobes curve gently for about half their 
width and then more rapidly to the lateral margins. Each segment is 
divided unequally by a furrow extending nearly from one margin of the 
thorax to the other. The posterior portion, which is the wider, bears 
numerous nodes, four of which occur on the axis and two or more on each 
pleura. The nodes on the pleurz are much larger than those on the axis 
and their location on different segments is not always uniform. The 


66 Frerp Museum or Natura History — Geotoey, Vor. IV. 


five anterior segments terminate at the lateral margins of the thorax, 
but the seven posterior ones are abruptly bent backward at the lateral 
thoracic margins and are produced into spines. The spines of the sixth 
segment extend more than one-third their length beyond the pygidium; 
the spines of the other segments are considerably shorter. 

Pygidium small but too poorly preserved in the specimens at hand 
for a detailed description. 

The dimensions of the type specimens are as follows: 

Length of the holotype along the axis 23.6 mm. Length of body, 
including pleural spines, 31.3 mm.; width at genal angles 19.6 mm.; 
length of cephalon, including genal spines, 16 mm.; length of glabella 7.8 
mm.; width of anterior portion of glabella 4.7 mm.; ditto across lateral 
lobes, 5.3 mm.; length of thorax 12.8 mm. 

Width of paratype at genal angles 27.8 mm.; length of glabella 10.7 
mm.; width of posterior portion 8.0 mm.; ditto across lateral lobes, 8.7 
mm. 

This description is based upon the holotype (Mus. No. P 16631, 
Pl. XVI, fig. 1), a nearly complete specimen, a practically complete 
cephalon (Mus. No. P 17039, Pl. XVI, figs. 2-3), somewhat larger than 
the holotype, and a detached free cheek with eye (Mus. No. P-16633, 
Pl. XVI, fig. 4). 

Localities and horizon.— The holotype was collected by the writer 
from the top of the Lower Maquoketa beds at Elgin, the two paratypes 
from a similar horizon at Bloomfield. More or less complete cranidia are 
not uncommon at a similar and somewhat lower horizon at Clermont. 


Family CALYMENID, Brongniart 
Genus CALYMENE Brongniart 1822. 


‘“Complete body sub-oval in outline, possessing the power of com- 
plete enrollment; cephalon sub-crescentiform with thickened margin, 
genal angles usually rounded; glabella strongly convex, narrowed in 
front, with three pairs of deep lateral furrows; occipital segment well 
defined; posterior limb of the facial sutures originating just in front of 
the genal angles; free cheeks elongate, separate, usually with a free plate 
between their anterior extremities in front of the glabella; eyes small; 
hypostoma sub-quadrate, notched. Thorax with thirteen segments; 
axis strongly convex and bounded by deep axial furrows; pleural lobes 
wider than the axis, bent down laterally. Pygidium distinctly marked 
off from the thorax, with six to eleven segments, axis prominent and 
margin entire.’ (Weller, Pal. Chicago Area, p. 261.) 


OcTOBER, 1913. New TRILOBITES — SLOCOM 67 


CALYMENE FAYETTENSIS sp. nov. Plate XVI, Figs. 8-9. 

Type specimen No. P 16755 Field Museum. 

Body strongly trilobate, subovate in outline, greatest breadth at the 
genal angles, narrowing gradually to the anterior border of the pygi- 
dium, thence abruptly to the posterior extremity of the pygidium. 
Surface finely papillose with small rounded tubercles more or less 
regularly distributed thereon. 

Cephalon sublunate in outline, anterior border arcuate, except 
between the anterior limbs of the facial sutures, where it is somewhat 
produced. Glabella moderately convex, not prominent anteriorly, 
slightly elevated above the cheeks, well defined by the dorsal furrows, 
broadest across the posterior lobes where the width nearly equals the 
length, gradually narrowing towards the front, which is truncated; 
frontal lobe quadrangular, occupying less than one-fourth the length of 
the glabella; first lateral lobes small, hardly separated from the frontal 
lobes; second lateral lobes larger and nodelike; posterior lobes much 
larger, forming a pair of conspicuous nodes at the base of the glabella. 
The lateral furrows do not cross the glabella, first pair indistinct, trans- 
verse; second pair well defined and bent backward; posterior pair 
broader and deeper than second pair, curved backward so as to nearly, 
but not quite, isolate the posterior lobes; occipital furrow arched forward 
in the middle, somewhat deeper and narrower back of the posterior gla- 
bella lobes, where it merges into the posterior cheek furrows; occipital 
segment prominent, widest in the middle, gradually narrowing to the 
dorsal furrows. Cheeks convex, with rounded lateral and sharp 
posterior marginal borders, greatest elevation at the palpebral lobes; 
marginal borders defined by shallow, concave furrows; free cheeks 
subtriangular, about half the size of the fixed cheeks. Facial sutures 
originate at the genal angles which they unequally bisect; from thence 
they pass obliquely forward until opposite the posterior glabella furrow; 
thence curve abruptly over the eye lobes to the anterior border, which 
they cut almost in front of the eyes. A small free plate to which the 
hypostoma is attached occupies the space between the anterior ex- 
tremities of the sutures. Eyes small, lenses not preserved, situated well 
forward, about opposite the second glabella furrows. 

Thorax composed of thirteen segments, length about three-fifths the 
entire length of the test, strongly trilobed; segments arched forward on 
the axis, each one bearing a pronounced rounded node on either side 
just within the dorsal furrows, and a smaller, more pointed one on each 
pleura, pointing forward, situated on the anterior margin at the crest of 
the convexity, when the body is rolled up; on the posterior margin is a 
notch or indentation into which the node from the next posterior seg- 


68 Frecp Museum or Naturat History —Grouocy, Vor. IV. 


ment fits; each pleura is provided with a well-marked groove which 
originates at the dorsal furrow and extends on to the flattened distal 
portion of the segment. The pleural segments curve regularly upward 
for about one-third their length, then abruptly to the lateral margins. 

Pygidium transversely suboval in outline with posterior portion pro- 
duced into an obtuse angle, strongly trilobed. The convex axis tapers 
posteriorly and terminates on a rounded extremity near the posterior 
margin, marked by seven annulations. The pleural lobes slope abruptly 
from the dorsal furrows to the margins, each lobe consisting of five or 
more segments, the anterior ones being distinct and the others becoming 
less so until they are entirely obsolete at the posterior extremity of the 
pygidium; each segment is marked by a shallow longitudinal groove 
which originates at the lateral margins and becomes obsolete before 
the dorsal furrow is reached. 

The dimensions of the type specimen are: Length of cephalon 10.5 


mm.; width 18.3 mm.; length of thorax 21.5 mm.; length of pygidium - 


3.5 mm.; width 9.3 mm.; entire length of the body 39 mm. measured 
around an enrolled specimen, but if the test was unrolled it would 
measure 3 or 4 mm. less. The cephalons of two specimens in the col- 
lection of Mr. A. G. Becker measure respectively 13.5 mm. long, 24 mm. 
wide, and 9.5 mm. long, 15.6 mm. wide. All of the specimens on which 
the description is based are enrolled specimens so that it is difficult to 
take accurate measurements of some of the parts. 

Remarks.— This species has been referred by most writers and 
collectors to C. senaria of the Ohio Valley region, but upon comparing 
practically perfect specimens from the two localities they are found to be 
distinct. The glabella in C. senaria is shorter and more convex, the 
pleural segments of the pygidium do not have a longitudinal furrow, 
the lip-like process on the anterior margin of the glabella is shorter and 
the surface of the test does not possess the rounded tubercles. C. mam- 
millata was described from the Maquoketa of Dubuque Co., Iowa, and 
specimens from the type locality loaned to the Museum for study from 
the collection of the State University of Iowa by Prof. George F. Kay 
prove C. fayettensis to be quite dissimilar. The frontal lip is very 
large in C. mammillata and bears a low, rounded tubercle just in front of 
each dorsal furrow. The surface ornamentation is also quite different. 
_C. fayettensis resembles C. christyi in the outlines of the glabella, but 
there the similarity ceases as it does not possess the genal spines or the 
curvature of the thoracic segments, and the form and size of the pygi- 
dium are entirely unlike. . The surface ornamentation of C. fayettensis 
is similar to that of C. niagarensis, but in the form of the glabella and 
many other characters it is entirely distinct. 


ee 


OcTOBER, I913. New TRILOBITES — SLOCOM 69 


Locality and horizon.— The type (Mus. No. P 16755) was col- 
lected by the writer in July, 1910, in the Lower Maquoketa shale 
at Clermont, Iowa. Other specimens were collected by the writer 
from the Lower Maquoketa beds at Clermont, Elgin, and Bloomfield, 
Iowa. 


CALYMENE GRACILIS sp. nov. Plate XVIII, Fig. 9. 


Type specimen No. P 17065 Field Museum. 

Body small, in form and general proportions similar to other species 
of the genus. The surface of the test appears smooth to the naked eye 
but under a magnifier it appears very finely papillose. 

Cephalon sublunate, width of the genal angles somewhat less than 
twice the length on the median line, about as 7:4. Anterior border 
flat, projecting obliquely forward and upward, not recurved; separated 
from the glabella by a deep, narrow, marginal furrow. The dorsal fur- 
rows, in passing forward from the occipital ring, diverge slightly near the 
posterior glabella lobes, then converge until they meet the anterior 
marginal furrow. Here the dorsal furrows become nearly obsolete on 
account of a large rounded node on each fixed cheek, opposite the 
anterior lobe of the glabella. Glabella convex, elevated above the 
cheeks, shorter than is usual in this genus, widest at the posterior lobes 
where the width is equal to the length, including the occipital ring, much 
narrower anteriorly; anterior lobe transverse, width less than one-third 
the length; first lateral lobes well defined, about the width of the ante- 
rior lobe and terminating about the same distance from the median line; 
second lateral lobes larger and node-like; posterior lateral lobes much 
larger, forming a pair of conspicuous nodes at the base of the glabella. 
Lateral furrows well defined but not crossing the glabella. The first 
pair transverse; second pair somewhat larger, but bent slightly back- 
ward; posterior pair broader and deeper, curved backward towards, but 
not reaching, the occipital furrow; at about two-thirds of their length 
from the dorsal furrows they bifurcate; the shorter fork extends toward 
the median line of the glabella, forming a well-defined node between the 
second and posterior lobes. The facial sutures originate just in front of 
the genal angles, curve forward and inward over the palpebral lobes 
and thence forward to the anterior margin. Occipital ring prominent, 
slightly wider in the middle, separated from the rest of the glabella by a 
well-defined occipital furrow. Cheeks only moderately convex aside 
from the palpebral lobes, which are long for this genus and rise very 
abruptly from the dorsal furrows; lateral marginal borders wide and 
well rounded, posterior border much narrower; all are defined by deep 
marginal furrows. 


70 Fretp Museum or Naturar History — Geotoey, Vor. IV. 


Thorax known only by a few detached segments which indicate that 
it was narrow and elevated. 

Pygidium subtriangular, terminating in a rounded obtuse angle, 
strongly elevated and trilobed. Axis convex, marked hy six or seven 
annulations; it tapers gradually and is truncated posteriorly so that the 
dorsal furrows instead of meeting at a point posteriorly are joined-by a 
short transverse furrow; the pleural lobes slope abruptly from the dorsal 
furrows to the margins; each lobe consists of five segments, faintly 
grooved on their distal portion; the segments merge into a smooth, 
undefined, marginal border. 

The type specimen is a perfect cranidium with the following dimen- 
sions: Length on median line 7.8 mm.; length including genal angles 
9.0 mm.; width 14.0 mm.; length of glabella including occipital ring 5.4 
mm.; length of glabella without occipital ring 4.5 mm.; width of gla- 
bella at anterior lobe 3.5 mm.; width of glabella at posterior lobes 5.4 
mm. A detached pygidium gives the following measurements: Length 
3.4 mm.; width 6.4 mm.; thickness 4.8 mm. 

Remarks.— This species was considered by Savage to be identical 


with Calymene fayettensis of the lower beds, but it is distinguished from. 


that species by its surface ornamentation, its shorter glabella, its larger 
anterior margin, its longer and more prominent palpebral lobes, the 
transverse furrow connecting the dorsal furrows on the pygidium and 
its smaller size. In surface ornamentation this species resembles C. 
senaria but is distinguished from it by its longer palpebral lobes, its 
relatively short and more elevated glabella. It is distinguished from 
all species known to the writer by the nodes, which are situated in the 
dorsal furrows on each side of the anterior lobe of the glabella. C. 
mammillata bears two nodes, but they are situated on the anterior 
margin. 

Locality and horizon.— Limestone layers of the Upper Maquoketa 
beds at Patterson’s Springs near Brainard, Iowa. No complete speci- 
mens have been observed by the writer, but cranidia, free cheeks, 
thoracic segments and pygidia are comparatively abundant. 


Family CHEIRURIDA, Salter. 
Genus CERAURUS Green 1832. 


“Entire body subovate in outline. Cephalon subsemicircular or 


subsemielliptical in outline, genal angles produced into spines; gla- 


bella strongly convex, broadest in front, with three pairs of deep lateral 


furrows; posterior limbs of the facial sutures cutting the lateral margins ~ 


- 


OcTOBER, 1913. NEw TRILOBITES — SLOCOM 71 


well in front of the genal angles; eyes small. Thorax usually with 
eleven segments, rarely nine to thirteen; axis prominent, narrower than 
the pleura, bounded by strong axial furrows. Pygidium small, pleural 
segments produced into points or spines.” (Weller, Pal. Chicago Area, 


p. 263.) 


CERAURUS PLEUREXANTHEMUS Green. 


1832. C. pleurexanthemus Green, No. Amer. Jour. Geol., Vol. I, p. 
560, pl. 14, fig. ro. 

1847. C. pleurexanthemus Hall, Pal. N. Y., Vol. I, p. 242, pls. 65-66. 

1847. C. pleurexanthemus S.A. Miller, Cin. Quar. Jour. Sci., Vol. I, 
p. 132. 

This species is said to occur in Fayette County, but so far has not 
been observed by the writer. A specimen in the collection of the 
University of Iowa appears to belong to this species. It is said to come 
from the Maquoketa beds of an adjoining county, but the exact data 
are missing. 


CERAURUS MILLERANUS Miller and Gurley. Plate XVII, Figs. 1-3. 


1894. C. milleranus Miller and Gurley, Bull. IIT, Ill. St. Mus. Nat. 
Hist., p. 80, pl. 8, fig. ro. 

Type specimen No. 6062 University of Chicago. 

General outline of the carapace, exclusive of the spines, subovate, 
abruptly narrowed posteriorly; moderately convex, trilobation distinct. 

Cephalon semielliptical, width nearly three times the length; dorsal 
furrows well marked. Glabella convex, narrower than the cheeks at 
the occipital ring, gradually widening anteriorly until its width about 
equals its length, abruptly bent downward at the frontal margin; 
anterior lobe constituting about one-third the length of the glabella; the 
three pairs of lateral furrows are short and about equidistant, forming 
three pairs of small convex lateral lobes; the two anterior pairs of fur- 
rows extend slightly forward, but the posterior pair is transverse for a 
part of its course and then bends abruptly backward until it meets the 
occipital furrow isolating the posterior lateral lobes. Occipital seg- 
ment arched upward, higher than the anterior portion of the glabella, 
greatest height at the posterior margin, sloping gradually into the 
occipital furrow. This furrow is narrow and deep behind the posterior 
lateral glabella lobes but wider and shallow in its median portion. 
Cheeks convex with well-defined rounded marginal borders, posterior 
angle produced into spines, which point backward; eyes prominent, 
globular, placed near the center of the cheeks; the palpebral lobes bear 
a pit near the base on the side nearest to the dorsal furrows; the facial 


72 Fierp Museum or Naturat History — Geotoey, Vor. IV. 


sutures originate on the lateral margins about in line with the occipital 
furrow, curve forward and inward to the palpebral lobes, which they 
traverse, thence pass forward with a sigmoid curve to the anterior mar- 
gin of the cephalon. 

Thorax composed of ten segments; axis convex, about the same 
width as the pleure; pleure flattened for one-third to one-half their 
width -from the dorsal furrows, then bent downward and backward, 
tapering to a point; each pleural segment is ornamented with a promi- 
nent tubercle situated near the point where the pleuree curve downward; 
an angular furrow originates on the anterior margin of each pleural seg- 
ment at the dorsal furrow and crosses it obliquely, reaching the posterior 
margin behind the tubercle; dorsal furrows distinct, nearly parallel 
from the first to the eighth thoracic segment, then converging poste- 
riorly. 

Pygidium short, much narrower than the posterior seoueue of the 
thorax, consisting of three segments; the anterior segment bears a pair 
of stout spines, which extend posteriorly with the points somewhat con- 
verging; axis undefined. 

Surface of the cephalon, within the marginal borders, covered with 
irregularly placed tubercles; on the cheeks the tubercles are somewhat 
farther apart and the interspaces are pitted; the marginal borders and 
genal spines are finely granulose; two or more conical tubercles are 
situated on the posterior borders of the cheeks; the entire thorax is 
finely granulose, as‘is also the pygidium, but the granulations are more 
conspicuous on the caudal spines. 

Measurements of the type are as follows: 


Length om anedian Wine s,s ices gs od daw ea edad 28.7 mm. 
Length including caudal spines... .. pip pita wee Pa lth aa 35-4 mm. 
Width eh cenal anew sieges pha baa gods ecw ae ee ges 21.6 mm. 
Width: at. pomté of getial soities (009 Sek Wi ein ees 23.6 mm. 
Length of cephalon including genal spines........... ... 11.5 mm. 
Lehoth of ola betas ii ects teed. ca cis Set hopies ta Atogeae ee 8.0 mm. 
Width of posterior lobes of glabella ..........5........ 6.0 mm. 
Width of anterior lobe of glabella..:.................6. 7.5 mm. 
Width of pygidium. ........60...5. roe ey ae RUE of 7.4 mm. 
Length OF py eine is es pape ee bs oS cus Siow ARs 2.7 mm. 


The above description is based on the type specimen from Cincin- 
nati, Ohio, No. 6062 of the paleontological collection of the University 
of Chicago. The species is known to the writer from Fayette County by 
twelve more or less complete cephalons and two pygidia. These agree 
with the type except that in the type the genal spines are somewhat 


shorter, the tubercles on the posterior border are less conspicuous ‘and — 


ea es 


i i ae 


OCTOBER, 1913. New TRILoBITES — SLocom 73 


the longitudinal curve of the glabella is somewhat more abrupt in front, 
making its anterior lobe appear shorter in dorsal view. This last 
feature may be due to-distortion. 

C. milleranus is distinguished from C. pleurexanthemus by its propor- 
tionally shorter cephalon, its less flaring genal spines, and by its eyes 
being globular and situated about equidistant from the dorsal furrows 
and from the posterior margin of the cephalon. The eyes of C. pleu- 
rexanthemus are conical and nearer the dorsal furrows. Further, the 
spines of the pygidium in C. milleranus converge at their points instead 
of diverging as in C. pleurexanthemus. 

Locality and horizon.— Lower Maquoketa shales of Clermont and 
Elgin, Iowa. 


CERAURUS ELGINENSIS sp. nov. Plate XVII, Figs. 4-5. 

Type specimens Nos. P 16630A, 16630B, 17030 Field Museum. 

Cephalon sublunate, width more than three times the length, 
anterior lateral margins arcuate, posterior margin transverse in the 
median portion, gently bent backward near the genal angles. Glabella 
convex, clavate, less than half the width of the cheeks at its posterior 
margin but gradually widening anteriorly until its width nearly equals 
its length; anterior lobe constituting about one-fourth the entire length 
of the glabella; three pairs of lateral furrows rather short, well defined, 
defining three pairs of convex lateral lobes, diminishing in size poste- 
riorly; the two anterior pairs of furrows are transverse, the posterior 
pair are transverse for part of their length, then bent backward until they 
join the occipital furrow, isolating the posterior lobes; occipital segment 
elevated at the posterior margin, sloping into the occipital furrow; 
occipital furrow shallow, concave in the median portion, narrower,: 
deeper and bent backward behind the glabella lobes; dorsal furrows 
deep, angular, forming deep angular pits where they merge into the 
marginal furrows; cheeks large, convex, posterior angles produced into 
long, stout spines, flattened anteriorly and pointing almost directly 


- backward; palpebral lobes elongated, large for the genus, placed well 


forward, about midway between the dorsal furrows and the lateral 
margins but nearer the posterior margins than the dorsal furrows. 
Near the base of each lobe on the side towards the dorsal furrow is 
situated a decided pit; an indistinct furrow extends from this pit to the 


~ crest of the lobes; the ocular ridges extend from the anterior angle of the 


palpebral lobes to the pit in the dorsal furrows; the facial sutures 


* originate on the lateral margins about in line with the posterior mar- 


ginal furrow, curve forward and inward to the palpebral lobes which 


they traverse, then forward to the anterior margin, which they reach in 


74 Fretp Museum oF Naturat History — Geovocy, Vor. IV. 


front of the glabella; marginal borders prominent, defined by shallow 
- furrows; the posterior furrows curve into the lateral furrows just within 
the genal angles; free cheeks small, less than one-third the size of the 
fixed cheeks. The surface of the glabella, with the exception of the 
occipital segment and the cheeks, is covered with more or less regularly 
distributed rounded tubercles; a larger, more conical tubercle is situated 
on each fixed cheek, just in front of the posterior furrow, at about one- 
third the distance from the dorsal furrow to the genal angle. A row of 
spine-like tubercles traverses the posterior marginal borders of the 
cheeks, and similar tubercles are distributed over the flattened portions 
of the genal spines, gradually diminishing in size posteriorly until they 
become obsolete. . 

Thorax not known. 

Pygidium transversely sub-elliptical in outline, aside from the spines 
length less than half the width; composed of three segments, the ex- 
tremities of the anterior segment produced into long, stout, flattened 
spines, which curve outward and backward; second and third segments 
much smaller; axis not well defined. The surface of the caudal spines 
is covered with sharp conical tubercles similar to those on the genal 
spines. The pygidium above described (Pl. XVII, fig. 5) was not 
associated with the cephalons but came: from the same horizon at 


Bloomfield. Its size and the form and ornamentation of the spines are ~ 


such as might accompany these cephalons and no other cephalons have 
been observed to which this pygidium could well be referred. 


Measurements P 16630A P 16630B 
Length of cephalon on median line.................. 13.7 mm. 12.3mm. 
Width of cephalon at genal angles.................. 3825.55 36.3. 
Width of cephalon including genal spines (estimated).. 4020-35, 38.07% 
Ue og ote) ats ea Fe ay VBE: VeRO ea MAAR aN Gee ed othe ceil Sera raha er pean Ra 13.07 5) im O46 aka 
Width of anterior lobe of glabella....:............0% TLs5o-o5 O,6a,% 
Width of posterior lobes of glabella.................. BES 62734 

P 17030 

Wacth of: py rica cote citas, eu i tet tannma ens ota eee tone 4s 10.7 mm. 
Length Of pypiaim, 25.05% bedi ais sc rede ie 2 ¥ oe Susu 
Length of caudal spines (estimated) . gen Nate Maa hens Monts ts 207.0850 


C. elginensis differs from all other species known to the writer in 
having extremely long genal spines with spinel-ike tubercles on their 
flattened portion. It is also distinguished from C. milleranus and C. 
pleurexanthemus by having the eyes farther apart. It is most nearly 
related to C. dentatus Raymond and Barton, but the ocular ridges are 
not present in that species and the eves are not so far forward. 
~ Locality and horizon.— The species is known to the writer from 


a a 


ee 


OcTOBER, 1913. New TRILOBITES — SLOCOM 75 


two cephalons from the top of the Lower Maquoketa beds at Elgin, 
Iowa, and a pygidium, which is referred with some doubt, from the 
same horizon at Bloomfield, Iowa. 


Genus ECCOPTOCHILE Corda 1847. 


Body subovate in outline. Cephalon subsemicircular. Genal 
angles produced into spines. Glabella of uniform width rounded and 
full in front, glabella furrows short, transverse, posterior glabella lobe 
isolated or nearly so. Eyes holochroal. Pygidium short with three 
annulations on the axis, pleural lobes produced into three pairs of flat 
digitate extensions, obtusely rounded at their extremities, which do 
not extend beyond the marginal arc. (Clarke, Pal. Minn., Vol. IIT, pt. 


2, p. 378.) 


EccoprocuILe ? MEEKANUuS* S. A. Miller. Plate XVII, Figs. 6-0. 


1873. Ceraurus icarus Meek, Pal. Ohio, Vol. I, p. 162, pl. 14, figs. 

11a-c. 

1889. Ceraurus meekanus S.A. M., N. Am. Geol. and Pal., p. 537. 

Type specimens Nos. 2409, 10837 University of Chicago. 

Body subovate in outline, moderately convex, distinctly trilobed. 
Surface smooth to the naked eye but under a magnifier the cephalon 
appears finely granulose. 

Cephalon subsemicircular, somewhat flattened anteriorly, genal 
angles produced into short spines, posterior margin nearly straight until 
it merges into the genal spines, where it is bent nearly at right angles 
(Pl. XVII, fig. 8). Glabella subquadrate, rounded in front, length in 
front of the occipital furrow about equal to the width, depressed convex. 
Anterior lobe of the glabella transversely oval, about twice as wide as 
long, lateral lobes nearly transverse and about equal in size. Glabella 
furrows distinct, length about one-third the width of the glabella, 
anterior pair bent backward; middle pair nearly at right angles to the 
axis of the glabella; posterior pair similar to the middle pair for most of 
the length but having the inner ends abruptly bent backward until 
_ they meet the occipital furrow, isolating the posterior glabella lobes; 
occipital segment arched upward somewhat higher than the rest of the 


: glabella, wider in the median portion, tapering towards the dorsal 


furrows; occipital furrow deep and narrow, arched forward. Dorsal 
_ furrows deep and narrow, diverging slightly at the posterior margin of 
the cephalon, thence passing to the front of the glabella, which they 


*As this paper is going to press, the writer is informed that a new genus has 
been made by Barton of which this species is the genotype. 


76 Fretp Museum or Natura History — Georoey, Vor. IV. 


surround, leaving a narrow anterior border. In each furrow just in 
front of the anterior glabella furrow is a distinct pit. Cheeks large, 
sloping anteriorly and laterally from the eyes; posterior cheek furrows 
narrow; near the genal angles they meet the lateral furrows, which are 
wider and extend forward parallel to the margins until they meet the 
dorsal furrows; marginal borders somewhat concave on account of 
shallow marginal furrows, which originate on the genal spines. Eyes of 
moderate size, situated opposite the second glabella furrows, visual 
surface sublunate, palpebral lobes moderately prominent, approaching 
in height that of the glabella. The facial sutures originate a short dis- 
tance in front of the genal angles, curve obliquely forward, then abruptly 
inward to the posterior angles of the eyes, follow the inner margin of the 
eyes and again forward with a broad curve, cutting the anterior margin | 
of the cephalon in front of the glabella (Pl. XVII, fig. 8.) 

Thorax somewhat longer than wide, consisting of eleven segments, 
distinctly trilobed. Axis narrower than the pleure, regularly arched 
upward. Pleural lobes flattened for about one-third their width, thence 
abruptly curved to their lateral margins; each segment marked by a 
deep groove across the axis; another smaller groove originates on the 
anterior margin of each pleura near the dorsal furrows and crosses the 
pleura obliquely; on the anterior margin of each pleura, near the point 
where the pleura is bent downward, a still smaller groove defines a low 
oblong node which points forward, not upward. The segments are 
nearly transverse across the axis and about half the length of the 
pleure; their distal portions curve gently backward to the falcate 
extremities. 

Pygidium small, transversely subelliptical, width more than twice 
the length, posterior curve much flattened. Axis small with three well 
defined annulations. Two shallow pits occur just back of the termina- 
tion of the axis. Pleural lobes large, composed of three segments which 
are produced posteriorly into flattened spines. The anterior pair is the 
largest; carinate on top, strongly curved backward and obtusely rounded 
at the extremities; the other two pair decrease in size inward and are 
more pointed. 

Remarks.— Of the specimens here figured and described, figs. 6 and 
7, are two views of an enrolled individual, complete with the exception 
of the genal spines, in the collection of Mr. A. G.-Becker, from the Lower 
Maquoketa shale, Clermont; while figs. 8 and 9 (Mus. No. P 11130) show 
specimens collected by the writer in the top of the Lower Maquoketa beds 
at Clermont. In fig. 8 the position of the facial suture and the angle 
formed by the posterior margin of the cephalon and the genal angles are 
well illustrated. In Meek’s original figure this angle is shown as a 


OcTOBER, 1913. New TRILoBItES — SLocom 77 


curve, but the type specimen, now in the paleontological collection of 
the University of Chicago, agrees with the specimen here described. 

Localities and horizons.— The type specimens were from the Rich- | 
mond beds in Butler County, Ohio, and Richmond, Indiana. The 
specimens here described are from the Lower Maquoketa beds, Cler- 
mont, Iowa. 


Genus SPHASROCORYPHE Angelin 1852. 


Cephalon convex, genal angles spined; glabella spheroidal anteriorly, 
lateral lobes obscure; eyes prominent; facial sutures cut the lateral and 
frontal margins. Thorax composed of 8-10 segments; axis narrower 
than the pleurz; pleural segments terminate in short reflexed spines. 
Pygidium composed of three segments, the extremities of the anterior 
one produced into long spines. Type S. granulata. Range Ordovician, 
Europe and North America. 


SPHHROCORYPHE MAQUOKETENSIS sp. nov. Plate XV, Figs. 1-4. 

Type specimens Nos. P 11152A, 11152B, 16954 and 17051 Field 
Museum. 

Cephalon sublunate in outline, convex, distinctly trilobed; anterior 
margin truncated; posterior margin nearly transverse. Glabella very 
prominent, anterior lobe globular, produced beyond the anterior mar- 
gin; comprising fully three-fourths the bulk of the glabella; a single 
pair of shallow, transverse, lateral furrows meet just behind the lateral 
lobe of the glabella and separate it from a pair of indistinct lateral 
lobes; occipital segment arched slightly forward, its posterior margin 
abruptly elevated, surface sloping into the furrow; occipital furrow 
shallow, not well-defined except at its extremities. Dorsal furrows 
well defined, much wider and deeper at the junctures with the occi- 
pital and glabella furrows, diverging somewhat in passing forward from 
the posterior margin of the cephalon until near the anterior margin 
where they abruptly converge until they meet forming the anterior 
marginal furrow; cheeks depressed convex, greatest. elevation at the 
palpebral lobes which are situated about midway between the posterior 
and anterior margins and one-third the distance from the dorsal fur- 
rows to the genal angles; antero-lateral margins of the cheeks forming 
an elongate sigmoid curve; free cheeks triangular, small, less than one- 
_ half the size of the fixed cheeks; eyes large, prominent, globular; the 
facial sutures originate on the lateral margins well in front of the genal 
angles, pass inward and slightly backward over the palpebral lobes, 
thence forward to the anterior margin; the genal angles merge into 
stout, recurved spines; the posterior marginal furrows are continuations 


78 Fretp Museum or Naturat History — Georoecy, Vor. IV. 


of the occipital furrow but narrower and deeper; they terminate abruptly 
before the genal angles are reached; a deep elongate pit on each fixed 
cheek and a longer, shallower one on each free cheek represent the 
lateral marginal furrows. 

Thorax not observed. 

Pygidium small, sub-triangular in outline, aside from the spines; not 
distinctly trilobed, composed of three segments; the first of these has its 


extremities produced into long, diverging, slightly recurved spines; . 


margin entire, with its ventral.surface forming a thick doublure. 
Surface of the globular portion of the glabella pustulose; pustules 
rounded, larger near the transverse glabella furrow and gradually dimin- 
ishing in size anteriorly; balance of cephalon smooth or finely granulose; 
surface of pygidium pustulose, pustules more prominent on the spines. 


Measurements of cephalon Pipes P 11152B 
Length on median line from posterior to anterior 
PRAT ONE elec r rice Setar covaettes wae oincmeheewlg hntsnoe ous ue shes 4.6 mm. 
Length from posterior margin to front of glabella. . 7.4mm. 10.4 mm. 
Length from front of glabella to points of spines. . 13.0 mm. 
Length of anterior lobe of glabella.............. 5.0mm. 7.7mm. 
Width of anterior lobe of glabella............... 4.7 mm. 7.5 mm. 
Width of cephalon at genal angles............... 10.2 mm. 14.6 mm. 
Width of cephalon at points of spines........... 15.8 mm. 
Lerigth of occipital segment: 05... ee 2.3 mm. 3.2 mms 
Width: of -oceipital seement 5.5. cose cies oto 1.0 mm. 1.2 mm. 
Measurements of pygidium P 16954 P 17051 
Wadthrot anterior: margin dose) no tole ena. tes 3.4 mm. 6.7 mm. 
Length on inedinte Lites 2.535 ae is sigicuns! 86 Fes58 they 1.5 mm. 3.2 mm. 
Vengtitneluding spines iss ast oa oc. Gao ee bs as 4.2 mm. -10.3 mm. 


This species is the most abundant trilobite in the shales of the 
Lower Maquoketa beds, but a great majority of the individuals are 
represented only by the globular portion of the glabella. They range 
in size from 2.5 mm. to 7.5 mm.in diameter. The writer was fortunate 
enough to obtain about twenty more or less complete cephalons and 
three pygidia. No thorax has been observed that can be referred to this 
species so that it is not certain that these pygidia belong to the cephalons, 
yet from their form and the conditions under which they were collected, 
there is little doubt that they belong to this species. 

S. maquoketensis differs from all previously described species in 
possessing large pits in place of the lateral marginal furrows. It re- 
sembles S. granulata Angelin in the form of the marginal outline, but in 
S. maquoketensis the cephalon is longer in proportion to the width and 
the pustules on the glabella are finer. S. salteri Billings is from a similar 
horizon, but in S. salteri the width of the glabella at its posterior margin 


OcTOBER, 1913. New TRILOBITES — SLOcoM 79 


is three-fourths of its greatest width, and it has tubercles at the juncture | 
of the occipital and dorsal furrows; in S. maquoketensis the glabella is 
‘twice as wide anteriorly as posteriorly and the tubercles are wanting. 

Localities and horizons.— Abundant in the top layers and some- 
what less so in the middle layers of the Lower Maquoketa shales of 
Clermont, Elgin, and Bloomfield, Iowa. 


Family PHACOPID, Salter. 
Genus PTERYGOMETOPUS Schmidt 1881. 


Cephalon obtusely angular in front. Glabella enlarging anteriorly, 
lateral furrows well defined. Eyes large, schizochroal. Posterior limb 
of the facial suture cuts the margin well in front of the genal angles, 
and the anterior limb crosses the lateral expansions of the frontal lobe 
of the glabella. Pygidium rounded, margin entire, without caudal 
spine. Range, Ordovician of Europe and North America. 


PTERYGOMETOPUS FREDRICKI sp. nov. Plate XVIII, Figs. 1-5. 


Type specimen No. P 17024 Field Museum. - 

Test elongate-ovate in outline, trilobation distinct. Cephalon sublu- 
- nate in outline, convex, anterior border rather thick and rounded, 
posterior margin concave, genal angles rounded. Glabella large, con- 
vex, greatest elevation and greatest width near the anterior margin, 
well defined by the dorsal furrows; anterior lobe large, transversely 
elliptical, rising abruptly from the anterior border; it comprises more 
than half of the glabella; anterior pair of lateral furrows originating at 
the anterior angles of the eyes, passing obliquely backward but not 
crossing the glabella; second pair of lateral furrows smaller than the 
first and directed obliquely forward forming a pair of triangular lateral 
lobes; the third pair of lateral furrows bifurcate, the anterior forks 
extending forward parallel to the second lateral furrows defining the 
quadrangular second lateral lobes, the posterior forks extending back- 
ward until they join the occipital furrow isolating the small, posterior, 
glabella lobes; occipital segment elevated at its posterior margin sloping 
to the occipital furrow; occipital furrow narrow, distinct. Dorsal fur- 
rows narrow and deep, nearly parallel from the posterior margin of the 
cephalon to the third, lateral glabella furrows, thence diverging to the 
antero-lateral margins. Cheeks slope regularly to the lateral margins; 
marginal borders wide at the genal angles narrowing in each direction, 
marginal furrows shallow on the lateral margins, deeper on the posterior 
margins; palpebral lobes large, prominent, but not equaling the glabella 


80 FreLtp Museum or Naturat History — Geotocy, Vor. IV. 


in height; marked by a distinct furrow just within and parallel to the 
borders of the eyes; eyes large, lunate, extending from the posterior 
cheek furrows to the anterior glabella furrows, eye facets arranged in 
vertical rows of five facets each; the facial sutures originate on the 
lateral margins in front of the genal angles, curve inward with a sigmoid 
curve to the posterior angles of the eyes, follow the inner margin of the 
eyes to their anterior angles and thence pass forward to the anterior 
margin of the cephalon. 

Thorax distinctly trilobed, composed of eleven segments. Axis 
convex, occupying somewhat more than one-third the width of the 
thorax; the pleural segments extend outward from the dorsal furrows 
for a little more than one-third their length, from which point they bend 
backward and abruptly downward to the lateral margins; extremities 
rounded; a straight groove originates near the anterior edge of each of 
the pleural segments at the dorsal furrows, extends slightly backward 

-and outward and becomes obsolete on.the flattened surface of each 
segment. The dorsal furrows converge slightly to the ninth thoracic 
segment, then more rapidly to the pygidium. 

Pygidium subsemicircular in outline, slightly produced posteriorly,. 
strongly trilobed. Axis narrow, convex, margins slightly incurved, 
abruptly rounded posteriorly; there are ten sinuous annulations; dorsal 
furrows narrow and deep, entirely surrounding the axis; the pleural 
lobes, consisting of six to eight segments, each bearing a median groove, 
curve slightly upward in their anterior portion, then downward to the 
margins. The segments are defined by grooves which are distinct in 
the anterior portion of the pygidium but gradually become obsolete 
posteriorly. This feature is more noticeable in young specimens. Both 
segmentation and median grooves become obsolete a short distance 
from the margins, thus leaving a smooth, undefined, marginal border. 

The surface of the thorax and pygidium appears smooth to the eye, 
but under a magnifier is finely punctate, without nodes or spines. The 
surface of the cephalon is pustulose, the pustules on the elabelta being 
somewhat more prominent than on other parts. 

The dimensions of the type specimen (Mus. No. P 17024) are as 
follows: Length, 24.2 mm.; width at genal angles 11.5 mm.; length of 
cephalon on median line 6.7 mm.; length including genal angles 7.4 mm.; 
length of thorax 11.5 mm.; length of pygidium 6 mm.; greatest width of 
pygidium 8.7 mm. A detached pygidium (Mus. No. P 16923A) 
measures, length 11.0 mm.; greatest width 14.6 mm.; it has ten annula- 
tions in the axis and eight segments in each pleural lobe, the last two 
being visible only with a magnifier. This is the largest pygidium 
observed and appears to belong to an old individual. 


OcTOBER, 1913. NEw TRILOBITES — SLOcOM eee Oy 


A small coiled specimen (Pl. XVIII, figs. 4-5) in the collection of 
Mr. A. G. Becker, found associated with typical specimens, is doubt- 
fully referred to this species. It differs from the type in having a 
smooth instead of a pustulose glabella and the pygidium appears to be 
shorter in proportion to its width. Considering these characters in 
connection with its small size, it is probable that they only indicate the 
immaturity of the specimen. Its dimensions are: Length of cephalon 
5 mm.; length of thorax 10.4 mm., length of pygidium 3.3 mm.; width 
at genal angles 6.8 mm.; width at anterior margin of pygidium 4.9 mm. 
_ PP. fredricki is distinguished from P. larrabeei by having five rows of 
eye facets instead of eight, by its more inflated anterior portion of the 
glabella, by its thicker and shorter anterior margin, by its shorter 
pygidium and fewer annulations on its axis, and by the anterior limbs 
of the facial suture being less divergent. So far as is known to the 
writer, the number of rows of eye facets has not previously been used as 
a specific character, but it seems to be a constant character in the thirty 
specimens of the two species which he has observed. Specimens of 
P. callicephalus from the Trenton of Ottawa, Canada, which appear 
to be typical, have eight: rows of eye facets. P. fredricki appears to be 
related to P. callicephalus, but aside from the eye facets, the glabella is 
more inflated anteriorly and the anterior margin is smaller and less 
angular in P. fredricki. 

The specific name is given in honor of Dr. Fredrick Becker, who was 


’ one of the first collectors of fossils in Fayette County and who gave the 


writer much valuable information as to localities. 

Localities and horizon.— The type is from the top of the Lower 
Maquoketa beds at Bloomfield, Iowa. The species has been observed 
in beds somewhat lower down at Clermont and at Postville Junction, 
Iowa. 


PTERYGOMETOPUS LARRABEEI sp. nov. Plate XVIII, Figs. 6-8. 


Type specimen No. P 11256 Field Museum. 
Cephalon sublunate in outline, anterior margin produced into a thin 
‘subangular lip, genal angles well back of the occipital ring, rounded. 
Glabella large, depressed, convex, about twice as wide in front as at 
the occipital ring, anterior lobe transversely elliptical sloping gently 
towards the front, comprising fully half the glabella; anterior pair of 
glabella furrows originating at the anterior angles of the eyes and pass- 
ing obliquely backward but not meeting at the median line of the gla- 
bella; second pair of glabella furrows shorter and shallower than the 
first, directed obliquely forward; third pair of glabella furrows directed 
towards the axis of the glabella for a short-distance, then bifurcating, 


82 Fretp Museum or Natura History — Greotocy, Vor. IV. 


the posterior forks bending abruptly backward and joining the occipital 
furrow leaving the small posterior lobes entirely detached; the anterior 
and larger forks bending obliquely forward defining the third glabella 
lobes; occipital segment wide, slightly rounded, of about uniform width 
until near the dorsal furrows where it is abruptly constricted; occipital 
furrow shallow but distinct. Dorsal furrows narrow and deep, nearly 
parallel from the posterior margin of the cephalon to the posterior 
glabella furrows, thence diverging in a regular curve to the anterior 
angle of the eyes where they become obsolete. Palpebral lobes large, 
prominent, exceeding the glabella in height, marked with a distinct 
furrow just within and parallel to the border of the eye; eyes large, 
lunate, extending from the posterior cheek furrows to the anterior fur- 
rows of the glabella; eye facets arranged in vertical rows of eight facets 
each; the cheeks curve regularly to the lateral margins, marginal bor- 
ders rather wide on their lateral margins, narrow on their posterior 
margins, marginal furrows shallow on their lateral margins, narrower and 
deeper on the posterior margins. The facial sutures originate on the 
lateral margins well in front of the genal angles, curve inward and 
_ backward to the posterior angles of the eyes, follow the inner margin of 
the eyes to their anterior angles and thence curve outward to the 
margin of the cephalon, almost in line with the anterior furrows of the 
glabella. Surface of the glabella distinctly pustulose; that of the 
palpebral lobes, cheeks, occipital ring and anterior projection finely 
granulose. : 

Thorax not known. 

Pygidium subtriangular, somewhat rounded posteriorly, distinctly 
trilobed. Axis narrow, convex, margin slightly incurved, abruptly 
rounded posteriorly; there are thirteen sinuous annulations; the dorsal 
furrows entirely surround the axis; the pleural lobes, marked by seven or 
eight segments each bearing a median groove for part of its length, curve 
regularly to the lateral margins; both segmentation and grooves become 
obsolete a short distance from the margin, leaving a plain, undefined 
marginal border. The entire surface of the pygidium is finely punctate. 

Measurements.— Type specimen (Mus. No. P 11256). Length of 
cephalon on median line 9.5 mm., length including genal angles ro mm., 
width of cephalon 14.5 mm.; length of pygidium 9.2 mm., width 10.6 
mm., width of axis on anterior margin of pygidium 3 mm., length of axis 


7 mm. Another complete cephalon gave the following: Length on — 


median line 11 mm., length including genal angles 12.5 mm., width 
17.5 mm. 

Remarks.— The above description is based on the type specimen 
(Mus. No. P 11256) consisting of a complete cephalon and a nearly com- 


ee eee ae 


OcTOBER, 1913. New TRILOBITES — SLOCOM 83 


plete pygidium. In general form this species resembles P. callicephalus 
but differs from it in the following characters: In P. larrabeei the 
cephalon is longer in proportion to the width; the cheeks do not curve so 
abruptly to the lateral margins; the glabella is less inflated anteriorly; 
_ the pygidium is longer and has more annulations and segments; the 
pustulose surface occurs only on the glabella; the surfaces of the pal- 
pebral lobes, occipital ring and cheeks are punctate. The pygidium of 
P. larrabeei appears to be midway between P. callicephalus and P. 
intermedius in form. The specific name is given in memory of the late 
Ex-Governor William Larrabee on whose property some of the speci- 
mens were collected. 

Locality and horizon.— More or less complete cephalons and 
pygidia are comparatively abundant in the Lower Maquoketa beds at 
Clermont, Elgin, and Bloomfield. The type specimen came from 
Clermont. 

ACKNOWLEDGMENTS 


The generic descriptions used in this paper have been derived from a 
number of sources. Where practicable a copy of the original description 
of the genus has been given; in other cases the best descriptions available 
have been used. In nearly all cases the descriptions have been rewrit- 
ten, but where copied due credit has been given. 

The writer is under obligations to Mr. A. G. Becker of Clermont for 
the loan of specimens and assistance given while in the field. Mr. 
Becker not only placed his private collection at the disposal of the 
writer, but spent much time with him in actual collecting and gave 
valuable information as to localities to be visited. Also to Prof. 
George F. Kay for the loan of specimens from the paleontological col- 
lections of the State University of Iowa, and to Prof. Stuart Weller of 
the University of Chicago for the loan of type specimens and publica- 
_ tions which materially aided in the preparation of this paper, grateful 
acknowledgments are given. 


th a 


EXPLANATION OF PLATE XIll 


IsOTELUS IOWENSIS, Owen, page 48. 
Fig. 1. View of the inner surface of the test, showing position of the facial 


suture. Mus. No. Pr1241. X I. 
Fig. 2. Ventral view of a cephalon in the paleontological collection of the State 


University of Iowa, showing form and position of the hypostoma and sutures. x 9/ 7. 


a Oe ea 


FIELD MUSEUM OF NATURAL HISTORY. GEOLOGY, VOL. IV, PL. XIill 


LIBRARY 
UNIVERSITY OF ILLINOIS 
URBANA 


VIX STAT AQ. MOM AmAsGXS " . 
42 99nq ..voa qe Eetaosa evreanvd ae dehic ; 


oe ae Sa a\s lod adi to walv Lard <8 
lssigoloicasieg edt nt eqytimag silt 


EXPLANATION OF PLATE XIV 


BUMASTUS BECKERI sp. nov., page 54. 
Fig. 1. Lateral view of the holotype. x 7/g. 
Figs. 2, 3. Dorsal and lateral views of the paratype in the paleontological 
collections of the State University of Iowa. X 4/3. 
Fig. 4. Dorsal view of the paratype. Mus. No. P 16708. x 7/g. 


. 


ee ee ee a ee ee ey ine ee eye eae 


MEGALASPIS BECKERI QM, sp. nov., page 50. 
Fig. 5. Dorsal view of the type specimen. X '4/rs. 


THALEOPS OVATA Conrad, page 56. 
Fig. 6. Cranidium. Mus. No. P 11259, Clermont. X 13/14. ; 
Fig. 7. Dorsal view of a nearly complete specimen from Mineral Point, Wis. 
No. 6901 University of Chicago. x 13/ 14. ; 
Fig. 8. Cephalon showing cheek spines, from Dixon, IIl., No. 12584 Daler 
of Chicago. X 13/z4. 


NILEus vicILANs Meek and Worthen, page 52. 
Figs. 9-15. Series illustrating variations in size. X I. 


XIV 


GEOLOGY, VOL. IV, PL. 


FIELD MUSEUM OF NATURAL HISTORY. 


LIBRARY 
UNIVERSITY OF ILLINOIS 
URBANA 


EXPLANATION OF PLATE XV 


SPHAEROCORYPHE MAQUOKETENSIS sp. nov., page 77. 
Figs. 1, 2. Dorsal and lateral views of the holotype. Mus. No.P 11152A. X9/s. 
Fig. 3. Dorsal view of pygidium from Elgin. Mus. No. P 16954. X 1. 
Fig. 4. Ventral view of a larger pygidium from Elgin. Mus. No. P 17051. X1. 


AMPHILICHAS RHINOCEROS sp. nov., page 58. 


Fig. 5. View of the inner surface of the shell of a cranidium. The type speci- 
men. Mus. No. P11181. x 9/7. 
Fig. 6. Outline restoration from the type specimen. xX °/ 7 


AMPHILICHAS CLERMONTENSIS sp. nov., page 59. 
Fig. 7. Dorsal view of the type specimen. Mus. No. P 11257. X 9/y. 


FIELD MUSEUM OF NATURAL HISTORY. 


GEOLOGY, VOL. IV, PL. 


XV 


LIBRARY - 
“UNIVERSITY OF ILLINOIS i 
URBANA , = a 


v 


EXPLANATION OF PLATE XVI 


CYBELOIDES IOWENSIS sp. nov., page 64. 
Fig. 1. The holotype. Mus. No. P 16631. X 5/4. 
Figs. 2, 3. Dorsal and anterior views of the paratype. Mus. No. P 17039. X 1. 


Fig. 4. A detached free cheek showing form and position of the eye. Mus. 
No. P 16633. X 5/4. 


ENCRINURUS PERNODOSUS sp. nov., page 61. 


ng 5,6. Dorsal and lateral views of the holotype. Mus. No. P 17038. 
X 3/2. 


Fig. 7. A detached pygidium. Mus. No. P 16930. X 1. 


CALYMENE FAYETTENSIS sp. nov., page 67. 


Figs. 8,9. Dorsal and lateral views of the type specimen. Mus. No. P 16755. 
x 3/ 2. 


FIELD MUSEUM OF NATURAL HISTORY. GEOLOGY, VOL. IV, PL. XVI 


LIBRARY 
UNIVERSITY OF ILLINOIS | . 
URBANA 7 | 


Se ce, ey ee a 


VOU .g2 BeMaumIa eve 
< .Aogddr I of avM 


EXPLANATION OF PLATE XVII 


CERAURUS MILLERANUS Miller and Gurley, page 71. 
Fig. 1. A complete cranidium. Mus. No. P 16853. X 1. 
Fig. 2. A pygidium with one spine missing. Mus. No. P 16925. X 1. 
Fig. 3. The type specimen. No. 6062 University of Chicago. X 1.” 


CERAURUS ELGINENSIS sp. nov., page 73. 


Fig. 4. The holotype. Mus. No. P 16630A. X 1. 
Fig. 5. A pygidium referred to this species. Mus. No. P 17030. X I. 


EcCOPTOCHILE? MEEKANUS §&. A. Miller, page 75. 
Figs. 6, 7. Two views of a coiled specimen in the collection of Mr. A. G. 
Becker. X I. 
Fig. 8. An imperfect cranidium showing the form of the facial suture-and the 
posterior margin. Mus. No. P 11150. X 1. 
Fig. 9. Ventral view of a complete pygidium. Mus. No. P1r150. X 1. 


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GEOLOGY, VOL. IV, PL. XVII 


FIELD MUSEUM OF NATURAL HISTORY. 


LIBRARY 
UNIVERSITY OF ILLINOIS 
URBANA 


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EXPLANATION OF PLATE XVIII 


PTERYGOMETOPUS FREDRICKI Sp. nov., page 79. 
Fig. 1. The type specimen. Mus. No. P 17024. X 3/2. 
Fig. 2. Dorsal view of the cephalon of the above. X 3/2. : 
Fig. 3. Outline drawing of a lateral view of the same showing the form of the 
glabella. x 3/2. 
Figs. 4,5. Dorsal and lateral views of a young specimen referred to this species, 
in the collection of Mr. A. G. Becker. X 3. ~ 


PTERYGOMETOPUS LARRABEEI sp. nov., page 81. 
Fig. 6. The holotype. Mus. No. P 11256. X 5/4. 
Fig. 7. Outline drawing of a lateral view of the same showing form of the gla- 
bella. xX 5/4. 
Fig. 8. Pygidium associated with the holotype. x 5/4. 


CALYMENE GRACILIS sp. nov., page 69. 
Fig.9. The type specimen. Mus. No. P 17065. X 5/4. 


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FIELD MUSEUM OF NATURAL HISTORY. GEOLOGY, VOL. IV, PL. XVIII 


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